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From c09d6b86750e45c22aab539c24a951f46a046e19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert-Andr=C3=A9=20Mauchin?= <zebob.m@gmail.com>
Date: Sat, 18 Dec 2021 01:52:22 +0100
Subject: [PATCH] Update versioneer.py to 0.21

---
 constantly/__init__.py |    5 +-
 constantly/_version.py |  396 +++++++++----
 versioneer.py          | 1284 ++++++++++++++++++++++++++--------------
 3 files changed, 1139 insertions(+), 546 deletions(-)

diff --git a/constantly/__init__.py b/constantly/__init__.py
index d9e6ec7..ed8adf3 100644
--- a/constantly/__init__.py
+++ b/constantly/__init__.py
@@ -5,9 +5,8 @@ from constantly._constants import (
     NamedConstant, Names, ValueConstant, Values, FlagConstant, Flags
 )
 
-from ._version import get_versions
-__version__ = get_versions()['version']
-del get_versions
+from . import _version
+__version__ = _version.get_versions()['version']
 
 __author__  = "Twisted Matrix Laboratories"
 __license__ = "MIT"
diff --git a/constantly/_version.py b/constantly/_version.py
index 030701f..a19b78f 100644
--- a/constantly/_version.py
+++ b/constantly/_version.py
@@ -5,32 +5,37 @@
 # directories (produced by setup.py build) will contain a much shorter file
 # that just contains the computed version number.
 
-# This file is released into the public domain. Generated by
-# versioneer-0.15 (https://github.com/warner/python-versioneer)
+# versioneer-0.21 (https://github.com/python-versioneer/python-versioneer)
+
+"""Git implementation of _version.py."""
 
 import errno
 import os
 import re
 import subprocess
 import sys
+from typing import Callable, Dict
 
 
 def get_keywords():
+    """Get the keywords needed to look up the version information."""
     # these strings will be replaced by git during git-archive.
     # setup.py/versioneer.py will grep for the variable names, so they must
     # each be defined on a line of their own. _version.py will just call
     # get_keywords().
     git_refnames = " (tag: 15.1.0)"
     git_full = "c8375a7e3431792ea1b1b44678f3f6878d5e8c9a"
-    keywords = {"refnames": git_refnames, "full": git_full}
+    git_date = "$Format:%ci$"
+    keywords = {"refnames": git_refnames, "full": git_full, "date": git_date}
     return keywords
 
 
 class VersioneerConfig:
-    pass
+    """Container for Versioneer configuration parameters."""
 
 
 def get_config():
+    """Create, populate and return the VersioneerConfig() object."""
     # these strings are filled in when 'setup.py versioneer' creates
     # _version.py
     cfg = VersioneerConfig()
@@ -44,15 +50,17 @@ def get_config():
 
 
 class NotThisMethod(Exception):
-    pass
+    """Exception raised if a method is not valid for the current scenario."""
 
 
-LONG_VERSION_PY = {}
-HANDLERS = {}
+LONG_VERSION_PY: Dict[str, str] = {}
+HANDLERS: Dict[str, Dict[str, Callable]] = {}
 
 
 def register_vcs_handler(vcs, method):  # decorator
+    """Create decorator to mark a method as the handler of a VCS."""
     def decorate(f):
+        """Store f in HANDLERS[vcs][method]."""
         if vcs not in HANDLERS:
             HANDLERS[vcs] = {}
         HANDLERS[vcs][method] = f
@@ -60,91 +68,121 @@ def register_vcs_handler(vcs, method):  # decorator
     return decorate
 
 
-def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False):
+def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False,
+                env=None):
+    """Call the given command(s)."""
     assert isinstance(commands, list)
-    p = None
-    for c in commands:
+    process = None
+    for command in commands:
         try:
-            dispcmd = str([c] + args)
+            dispcmd = str([command] + args)
             # remember shell=False, so use git.cmd on windows, not just git
-            p = subprocess.Popen([c] + args, cwd=cwd, stdout=subprocess.PIPE,
-                                 stderr=(subprocess.PIPE if hide_stderr
-                                         else None))
+            process = subprocess.Popen([command] + args, cwd=cwd, env=env,
+                                       stdout=subprocess.PIPE,
+                                       stderr=(subprocess.PIPE if hide_stderr
+                                               else None))
             break
-        except EnvironmentError:
+        except OSError:
             e = sys.exc_info()[1]
             if e.errno == errno.ENOENT:
                 continue
             if verbose:
                 print("unable to run %s" % dispcmd)
                 print(e)
-            return None
+            return None, None
     else:
         if verbose:
             print("unable to find command, tried %s" % (commands,))
-        return None
-    stdout = p.communicate()[0].strip()
-    if sys.version_info[0] >= 3:
-        stdout = stdout.decode()
-    if p.returncode != 0:
+        return None, None
+    stdout = process.communicate()[0].strip().decode()
+    if process.returncode != 0:
         if verbose:
             print("unable to run %s (error)" % dispcmd)
-        return None
-    return stdout
+            print("stdout was %s" % stdout)
+        return None, process.returncode
+    return stdout, process.returncode
 
 
 def versions_from_parentdir(parentdir_prefix, root, verbose):
-    # Source tarballs conventionally unpack into a directory that includes
-    # both the project name and a version string.
-    dirname = os.path.basename(root)
-    if not dirname.startswith(parentdir_prefix):
-        if verbose:
-            print("guessing rootdir is '%s', but '%s' doesn't start with "
-                  "prefix '%s'" % (root, dirname, parentdir_prefix))
-        raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
-    return {"version": dirname[len(parentdir_prefix):],
-            "full-revisionid": None,
-            "dirty": False, "error": None}
+    """Try to determine the version from the parent directory name.
+
+    Source tarballs conventionally unpack into a directory that includes both
+    the project name and a version string. We will also support searching up
+    two directory levels for an appropriately named parent directory
+    """
+    rootdirs = []
+
+    for _ in range(3):
+        dirname = os.path.basename(root)
+        if dirname.startswith(parentdir_prefix):
+            return {"version": dirname[len(parentdir_prefix):],
+                    "full-revisionid": None,
+                    "dirty": False, "error": None, "date": None}
+        rootdirs.append(root)
+        root = os.path.dirname(root)  # up a level
+
+    if verbose:
+        print("Tried directories %s but none started with prefix %s" %
+              (str(rootdirs), parentdir_prefix))
+    raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
 
 
 @register_vcs_handler("git", "get_keywords")
 def git_get_keywords(versionfile_abs):
+    """Extract version information from the given file."""
     # the code embedded in _version.py can just fetch the value of these
     # keywords. When used from setup.py, we don't want to import _version.py,
     # so we do it with a regexp instead. This function is not used from
     # _version.py.
     keywords = {}
     try:
-        f = open(versionfile_abs, "r")
-        for line in f.readlines():
-            if line.strip().startswith("git_refnames ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["refnames"] = mo.group(1)
-            if line.strip().startswith("git_full ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["full"] = mo.group(1)
-        f.close()
-    except EnvironmentError:
+        with open(versionfile_abs, "r") as fobj:
+            for line in fobj:
+                if line.strip().startswith("git_refnames ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["refnames"] = mo.group(1)
+                if line.strip().startswith("git_full ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["full"] = mo.group(1)
+                if line.strip().startswith("git_date ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["date"] = mo.group(1)
+    except OSError:
         pass
     return keywords
 
 
 @register_vcs_handler("git", "keywords")
 def git_versions_from_keywords(keywords, tag_prefix, verbose):
-    if not keywords:
-        raise NotThisMethod("no keywords at all, weird")
+    """Get version information from git keywords."""
+    if "refnames" not in keywords:
+        raise NotThisMethod("Short version file found")
+    date = keywords.get("date")
+    if date is not None:
+        # Use only the last line.  Previous lines may contain GPG signature
+        # information.
+        date = date.splitlines()[-1]
+
+        # git-2.2.0 added "%cI", which expands to an ISO-8601 -compliant
+        # datestamp. However we prefer "%ci" (which expands to an "ISO-8601
+        # -like" string, which we must then edit to make compliant), because
+        # it's been around since git-1.5.3, and it's too difficult to
+        # discover which version we're using, or to work around using an
+        # older one.
+        date = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
     refnames = keywords["refnames"].strip()
     if refnames.startswith("$Format"):
         if verbose:
             print("keywords are unexpanded, not using")
         raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
-    refs = set([r.strip() for r in refnames.strip("()").split(",")])
+    refs = {r.strip() for r in refnames.strip("()").split(",")}
     # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
     # just "foo-1.0". If we see a "tag: " prefix, prefer those.
     TAG = "tag: "
-    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
+    tags = {r[len(TAG):] for r in refs if r.startswith(TAG)}
     if not tags:
         # Either we're using git < 1.8.3, or there really are no tags. We use
         # a heuristic: assume all version tags have a digit. The old git %d
@@ -153,54 +191,67 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         # between branches and tags. By ignoring refnames without digits, we
         # filter out many common branch names like "release" and
         # "stabilization", as well as "HEAD" and "master".
-        tags = set([r for r in refs if re.search(r'\d', r)])
+        tags = {r for r in refs if re.search(r'\d', r)}
         if verbose:
-            print("discarding '%s', no digits" % ",".join(refs-tags))
+            print("discarding '%s', no digits" % ",".join(refs - tags))
     if verbose:
         print("likely tags: %s" % ",".join(sorted(tags)))
     for ref in sorted(tags):
         # sorting will prefer e.g. "2.0" over "2.0rc1"
         if ref.startswith(tag_prefix):
             r = ref[len(tag_prefix):]
+            # Filter out refs that exactly match prefix or that don't start
+            # with a number once the prefix is stripped (mostly a concern
+            # when prefix is '')
+            if not re.match(r'\d', r):
+                continue
             if verbose:
                 print("picking %s" % r)
             return {"version": r,
                     "full-revisionid": keywords["full"].strip(),
-                    "dirty": False, "error": None
-                    }
+                    "dirty": False, "error": None,
+                    "date": date}
     # no suitable tags, so version is "0+unknown", but full hex is still there
     if verbose:
         print("no suitable tags, using unknown + full revision id")
     return {"version": "0+unknown",
             "full-revisionid": keywords["full"].strip(),
-            "dirty": False, "error": "no suitable tags"}
+            "dirty": False, "error": "no suitable tags", "date": None}
 
 
 @register_vcs_handler("git", "pieces_from_vcs")
-def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
-    # this runs 'git' from the root of the source tree. This only gets called
-    # if the git-archive 'subst' keywords were *not* expanded, and
-    # _version.py hasn't already been rewritten with a short version string,
-    # meaning we're inside a checked out source tree.
-
-    if not os.path.exists(os.path.join(root, ".git")):
-        if verbose:
-            print("no .git in %s" % root)
-        raise NotThisMethod("no .git directory")
+def git_pieces_from_vcs(tag_prefix, root, verbose, runner=run_command):
+    """Get version from 'git describe' in the root of the source tree.
 
+    This only gets called if the git-archive 'subst' keywords were *not*
+    expanded, and _version.py hasn't already been rewritten with a short
+    version string, meaning we're inside a checked out source tree.
+    """
     GITS = ["git"]
+    TAG_PREFIX_REGEX = "*"
     if sys.platform == "win32":
         GITS = ["git.cmd", "git.exe"]
-    # if there is a tag, this yields TAG-NUM-gHEX[-dirty]
-    # if there are no tags, this yields HEX[-dirty] (no NUM)
-    describe_out = run_command(GITS, ["describe", "--tags", "--dirty",
-                                      "--always", "--long"],
-                               cwd=root)
+        TAG_PREFIX_REGEX = r"\*"
+
+    _, rc = runner(GITS, ["rev-parse", "--git-dir"], cwd=root,
+                   hide_stderr=True)
+    if rc != 0:
+        if verbose:
+            print("Directory %s not under git control" % root)
+        raise NotThisMethod("'git rev-parse --git-dir' returned error")
+
+    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
+    # if there isn't one, this yields HEX[-dirty] (no NUM)
+    describe_out, rc = runner(GITS, ["describe", "--tags", "--dirty",
+                                     "--always", "--long",
+                                     "--match",
+                                     "%s%s" % (tag_prefix, TAG_PREFIX_REGEX)],
+                              cwd=root)
     # --long was added in git-1.5.5
     if describe_out is None:
         raise NotThisMethod("'git describe' failed")
     describe_out = describe_out.strip()
-    full_out = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
+    full_out, rc = runner(GITS, ["rev-parse", "HEAD"], cwd=root)
     if full_out is None:
         raise NotThisMethod("'git rev-parse' failed")
     full_out = full_out.strip()
@@ -210,6 +261,39 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     pieces["short"] = full_out[:7]  # maybe improved later
     pieces["error"] = None
 
+    branch_name, rc = runner(GITS, ["rev-parse", "--abbrev-ref", "HEAD"],
+                             cwd=root)
+    # --abbrev-ref was added in git-1.6.3
+    if rc != 0 or branch_name is None:
+        raise NotThisMethod("'git rev-parse --abbrev-ref' returned error")
+    branch_name = branch_name.strip()
+
+    if branch_name == "HEAD":
+        # If we aren't exactly on a branch, pick a branch which represents
+        # the current commit. If all else fails, we are on a branchless
+        # commit.
+        branches, rc = runner(GITS, ["branch", "--contains"], cwd=root)
+        # --contains was added in git-1.5.4
+        if rc != 0 or branches is None:
+            raise NotThisMethod("'git branch --contains' returned error")
+        branches = branches.split("\n")
+
+        # Remove the first line if we're running detached
+        if "(" in branches[0]:
+            branches.pop(0)
+
+        # Strip off the leading "* " from the list of branches.
+        branches = [branch[2:] for branch in branches]
+        if "master" in branches:
+            branch_name = "master"
+        elif not branches:
+            branch_name = None
+        else:
+            # Pick the first branch that is returned. Good or bad.
+            branch_name = branches[0]
+
+    pieces["branch"] = branch_name
+
     # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
     # TAG might have hyphens.
     git_describe = describe_out
@@ -226,7 +310,7 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
         # TAG-NUM-gHEX
         mo = re.search(r'^(.+)-(\d+)-g([0-9a-f]+)$', git_describe)
         if not mo:
-            # unparseable. Maybe git-describe is misbehaving?
+            # unparsable. Maybe git-describe is misbehaving?
             pieces["error"] = ("unable to parse git-describe output: '%s'"
                                % describe_out)
             return pieces
@@ -251,27 +335,35 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     else:
         # HEX: no tags
         pieces["closest-tag"] = None
-        count_out = run_command(GITS, ["rev-list", "HEAD", "--count"],
-                                cwd=root)
+        count_out, rc = runner(GITS, ["rev-list", "HEAD", "--count"], cwd=root)
         pieces["distance"] = int(count_out)  # total number of commits
 
+    # commit date: see ISO-8601 comment in git_versions_from_keywords()
+    date = runner(GITS, ["show", "-s", "--format=%ci", "HEAD"], cwd=root)[0].strip()
+    # Use only the last line.  Previous lines may contain GPG signature
+    # information.
+    date = date.splitlines()[-1]
+    pieces["date"] = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
+
     return pieces
 
 
 def plus_or_dot(pieces):
+    """Return a + if we don't already have one, else return a ."""
     if "+" in pieces.get("closest-tag", ""):
         return "."
     return "+"
 
 
 def render_pep440(pieces):
-    # now build up version string, with post-release "local version
-    # identifier". Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
-    # get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
+    """Build up version string, with post-release "local version identifier".
 
-    # exceptions:
-    # 1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
+    get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
 
+    Exceptions:
+    1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -288,31 +380,80 @@ def render_pep440(pieces):
     return rendered
 
 
-def render_pep440_pre(pieces):
-    # TAG[.post.devDISTANCE] . No -dirty
+def render_pep440_branch(pieces):
+    """TAG[[.dev0]+DISTANCE.gHEX[.dirty]] .
 
-    # exceptions:
-    # 1: no tags. 0.post.devDISTANCE
+    The ".dev0" means not master branch. Note that .dev0 sorts backwards
+    (a feature branch will appear "older" than the master branch).
 
+    Exceptions:
+    1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0"
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+untagged.%d.g%s" % (pieces["distance"],
+                                          pieces["short"])
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
+def pep440_split_post(ver):
+    """Split pep440 version string at the post-release segment.
+
+    Returns the release segments before the post-release and the
+    post-release version number (or -1 if no post-release segment is present).
+    """
+    vc = str.split(ver, ".post")
+    return vc[0], int(vc[1] or 0) if len(vc) == 2 else None
+
+
+def render_pep440_pre(pieces):
+    """TAG[.postN.devDISTANCE] -- No -dirty.
+
+    Exceptions:
+    1: no tags. 0.post0.devDISTANCE
+    """
+    if pieces["closest-tag"]:
         if pieces["distance"]:
-            rendered += ".post.dev%d" % pieces["distance"]
+            # update the post release segment
+            tag_version, post_version = pep440_split_post(pieces["closest-tag"])
+            rendered = tag_version
+            if post_version is not None:
+                rendered += ".post%d.dev%d" % (post_version+1, pieces["distance"])
+            else:
+                rendered += ".post0.dev%d" % (pieces["distance"])
+        else:
+            # no commits, use the tag as the version
+            rendered = pieces["closest-tag"]
     else:
         # exception #1
-        rendered = "0.post.dev%d" % pieces["distance"]
+        rendered = "0.post0.dev%d" % pieces["distance"]
     return rendered
 
 
 def render_pep440_post(pieces):
-    # TAG[.postDISTANCE[.dev0]+gHEX] . The ".dev0" means dirty. Note that
-    # .dev0 sorts backwards (a dirty tree will appear "older" than the
-    # corresponding clean one), but you shouldn't be releasing software with
-    # -dirty anyways.
+    """TAG[.postDISTANCE[.dev0]+gHEX] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty. Note that .dev0 sorts backwards
+    (a dirty tree will appear "older" than the corresponding clean one),
+    but you shouldn't be releasing software with -dirty anyways.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -330,12 +471,43 @@ def render_pep440_post(pieces):
     return rendered
 
 
+def render_pep440_post_branch(pieces):
+    """TAG[.postDISTANCE[.dev0]+gHEX[.dirty]] .
+
+    The ".dev0" means not master branch.
+
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]+gHEX[.dirty]
+    """
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".post%d" % pieces["distance"]
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "g%s" % pieces["short"]
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0.post%d" % pieces["distance"]
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+g%s" % pieces["short"]
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
 def render_pep440_old(pieces):
-    # TAG[.postDISTANCE[.dev0]] . The ".dev0" means dirty.
+    """TAG[.postDISTANCE[.dev0]] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -351,12 +523,13 @@ def render_pep440_old(pieces):
 
 
 def render_git_describe(pieces):
-    # TAG[-DISTANCE-gHEX][-dirty], like 'git describe --tags --dirty
-    # --always'
+    """TAG[-DISTANCE-gHEX][-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always'.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"]:
@@ -370,12 +543,14 @@ def render_git_describe(pieces):
 
 
 def render_git_describe_long(pieces):
-    # TAG-DISTANCE-gHEX[-dirty], like 'git describe --tags --dirty
-    # --always -long'. The distance/hash is unconditional.
+    """TAG-DISTANCE-gHEX[-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always -long'.
+    The distance/hash is unconditional.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         rendered += "-%d-g%s" % (pieces["distance"], pieces["short"])
@@ -388,21 +563,27 @@ def render_git_describe_long(pieces):
 
 
 def render(pieces, style):
+    """Render the given version pieces into the requested style."""
     if pieces["error"]:
         return {"version": "unknown",
                 "full-revisionid": pieces.get("long"),
                 "dirty": None,
-                "error": pieces["error"]}
+                "error": pieces["error"],
+                "date": None}
 
     if not style or style == "default":
         style = "pep440"  # the default
 
     if style == "pep440":
         rendered = render_pep440(pieces)
+    elif style == "pep440-branch":
+        rendered = render_pep440_branch(pieces)
     elif style == "pep440-pre":
         rendered = render_pep440_pre(pieces)
     elif style == "pep440-post":
         rendered = render_pep440_post(pieces)
+    elif style == "pep440-post-branch":
+        rendered = render_pep440_post_branch(pieces)
     elif style == "pep440-old":
         rendered = render_pep440_old(pieces)
     elif style == "git-describe":
@@ -413,10 +594,12 @@ def render(pieces, style):
         raise ValueError("unknown style '%s'" % style)
 
     return {"version": rendered, "full-revisionid": pieces["long"],
-            "dirty": pieces["dirty"], "error": None}
+            "dirty": pieces["dirty"], "error": None,
+            "date": pieces.get("date")}
 
 
 def get_versions():
+    """Get version information or return default if unable to do so."""
     # I am in _version.py, which lives at ROOT/VERSIONFILE_SOURCE. If we have
     # __file__, we can work backwards from there to the root. Some
     # py2exe/bbfreeze/non-CPython implementations don't do __file__, in which
@@ -436,12 +619,13 @@ def get_versions():
         # versionfile_source is the relative path from the top of the source
         # tree (where the .git directory might live) to this file. Invert
         # this to find the root from __file__.
-        for i in cfg.versionfile_source.split('/'):
+        for _ in cfg.versionfile_source.split('/'):
             root = os.path.dirname(root)
     except NameError:
         return {"version": "0+unknown", "full-revisionid": None,
                 "dirty": None,
-                "error": "unable to find root of source tree"}
+                "error": "unable to find root of source tree",
+                "date": None}
 
     try:
         pieces = git_pieces_from_vcs(cfg.tag_prefix, root, verbose)
@@ -457,4 +641,4 @@ def get_versions():
 
     return {"version": "0+unknown", "full-revisionid": None,
             "dirty": None,
-            "error": "unable to compute version"}
+            "error": "unable to compute version", "date": None}
diff --git a/versioneer.py b/versioneer.py
index c010f63..b4cd1d6 100644
--- a/versioneer.py
+++ b/versioneer.py
@@ -1,21 +1,18 @@
 
-# Version: 0.15
+# Version: 0.21
+
+"""The Versioneer - like a rocketeer, but for versions.
 
-"""
 The Versioneer
 ==============
 
 * like a rocketeer, but for versions!
-* https://github.com/warner/python-versioneer
+* https://github.com/python-versioneer/python-versioneer
 * Brian Warner
 * License: Public Domain
-* Compatible With: python2.6, 2.7, 3.2, 3.3, 3.4, and pypy
-* [![Latest Version]
-(https://pypip.in/version/versioneer/badge.svg?style=flat)
-](https://pypi.python.org/pypi/versioneer/)
-* [![Build Status]
-(https://travis-ci.org/warner/python-versioneer.png?branch=master)
-](https://travis-ci.org/warner/python-versioneer)
+* Compatible with: Python 3.6, 3.7, 3.8, 3.9 and pypy3
+* [![Latest Version][pypi-image]][pypi-url]
+* [![Build Status][travis-image]][travis-url]
 
 This is a tool for managing a recorded version number in distutils-based
 python projects. The goal is to remove the tedious and error-prone "update
@@ -26,9 +23,10 @@ system, and maybe making new tarballs.
 
 ## Quick Install
 
-* `pip install versioneer` to somewhere to your $PATH
-* add a `[versioneer]` section to your setup.cfg (see below)
+* `pip install versioneer` to somewhere in your $PATH
+* add a `[versioneer]` section to your setup.cfg (see [Install](INSTALL.md))
 * run `versioneer install` in your source tree, commit the results
+* Verify version information with `python setup.py version`
 
 ## Version Identifiers
 
@@ -60,7 +58,7 @@ version 1.3). Many VCS systems can report a description that captures this,
 for example `git describe --tags --dirty --always` reports things like
 "0.7-1-g574ab98-dirty" to indicate that the checkout is one revision past the
 0.7 tag, has a unique revision id of "574ab98", and is "dirty" (it has
-uncommitted changes.
+uncommitted changes).
 
 The version identifier is used for multiple purposes:
 
@@ -87,125 +85,7 @@ the generated version data.
 
 ## Installation
 
-First, decide on values for the following configuration variables:
-
-* `VCS`: the version control system you use. Currently accepts "git".
-
-* `style`: the style of version string to be produced. See "Styles" below for
-  details. Defaults to "pep440", which looks like
-  `TAG[+DISTANCE.gSHORTHASH[.dirty]]`.
-
-* `versionfile_source`:
-
-  A project-relative pathname into which the generated version strings should
-  be written. This is usually a `_version.py` next to your project's main
-  `__init__.py` file, so it can be imported at runtime. If your project uses
-  `src/myproject/__init__.py`, this should be `src/myproject/_version.py`.
-  This file should be checked in to your VCS as usual: the copy created below
-  by `setup.py setup_versioneer` will include code that parses expanded VCS
-  keywords in generated tarballs. The 'build' and 'sdist' commands will
-  replace it with a copy that has just the calculated version string.
-
-  This must be set even if your project does not have any modules (and will
-  therefore never import `_version.py`), since "setup.py sdist" -based trees
-  still need somewhere to record the pre-calculated version strings. Anywhere
-  in the source tree should do. If there is a `__init__.py` next to your
-  `_version.py`, the `setup.py setup_versioneer` command (described below)
-  will append some `__version__`-setting assignments, if they aren't already
-  present.
-
-* `versionfile_build`:
-
-  Like `versionfile_source`, but relative to the build directory instead of
-  the source directory. These will differ when your setup.py uses
-  'package_dir='. If you have `package_dir={'myproject': 'src/myproject'}`,
-  then you will probably have `versionfile_build='myproject/_version.py'` and
-  `versionfile_source='src/myproject/_version.py'`.
-
-  If this is set to None, then `setup.py build` will not attempt to rewrite
-  any `_version.py` in the built tree. If your project does not have any
-  libraries (e.g. if it only builds a script), then you should use
-  `versionfile_build = None` and override `distutils.command.build_scripts`
-  to explicitly insert a copy of `versioneer.get_version()` into your
-  generated script.
-
-* `tag_prefix`:
-
-  a string, like 'PROJECTNAME-', which appears at the start of all VCS tags.
-  If your tags look like 'myproject-1.2.0', then you should use
-  tag_prefix='myproject-'. If you use unprefixed tags like '1.2.0', this
-  should be an empty string.
-
-* `parentdir_prefix`:
-
-  a optional string, frequently the same as tag_prefix, which appears at the
-  start of all unpacked tarball filenames. If your tarball unpacks into
-  'myproject-1.2.0', this should be 'myproject-'. To disable this feature,
-  just omit the field from your `setup.cfg`.
-
-This tool provides one script, named `versioneer`. That script has one mode,
-"install", which writes a copy of `versioneer.py` into the current directory
-and runs `versioneer.py setup` to finish the installation.
-
-To versioneer-enable your project:
-
-* 1: Modify your `setup.cfg`, adding a section named `[versioneer]` and
-  populating it with the configuration values you decided earlier (note that
-  the option names are not case-sensitive):
-
-  ````
-  [versioneer]
-  VCS = git
-  style = pep440
-  versionfile_source = src/myproject/_version.py
-  versionfile_build = myproject/_version.py
-  tag_prefix = ""
-  parentdir_prefix = myproject-
-  ````
-
-* 2: Run `versioneer install`. This will do the following:
-
-  * copy `versioneer.py` into the top of your source tree
-  * create `_version.py` in the right place (`versionfile_source`)
-  * modify your `__init__.py` (if one exists next to `_version.py`) to define
-    `__version__` (by calling a function from `_version.py`)
-  * modify your `MANIFEST.in` to include both `versioneer.py` and the
-    generated `_version.py` in sdist tarballs
-
-  `versioneer install` will complain about any problems it finds with your
-  `setup.py` or `setup.cfg`. Run it multiple times until you have fixed all
-  the problems.
-
-* 3: add a `import versioneer` to your setup.py, and add the following
-  arguments to the setup() call:
-
-        version=versioneer.get_version(),
-        cmdclass=versioneer.get_cmdclass(),
-
-* 4: commit these changes to your VCS. To make sure you won't forget,
-  `versioneer install` will mark everything it touched for addition using
-  `git add`. Don't forget to add `setup.py` and `setup.cfg` too.
-
-## Post-Installation Usage
-
-Once established, all uses of your tree from a VCS checkout should get the
-current version string. All generated tarballs should include an embedded
-version string (so users who unpack them will not need a VCS tool installed).
-
-If you distribute your project through PyPI, then the release process should
-boil down to two steps:
-
-* 1: git tag 1.0
-* 2: python setup.py register sdist upload
-
-If you distribute it through github (i.e. users use github to generate
-tarballs with `git archive`), the process is:
-
-* 1: git tag 1.0
-* 2: git push; git push --tags
-
-Versioneer will report "0+untagged.NUMCOMMITS.gHASH" until your tree has at
-least one tag in its history.
+See [INSTALL.md](./INSTALL.md) for detailed installation instructions.
 
 ## Version-String Flavors
 
@@ -226,6 +106,10 @@ information:
 * `['full-revisionid']`: detailed revision identifier. For Git, this is the
   full SHA1 commit id, e.g. "1076c978a8d3cfc70f408fe5974aa6c092c949ac".
 
+* `['date']`: Date and time of the latest `HEAD` commit. For Git, it is the
+  commit date in ISO 8601 format. This will be None if the date is not
+  available.
+
 * `['dirty']`: a boolean, True if the tree has uncommitted changes. Note that
   this is only accurate if run in a VCS checkout, otherwise it is likely to
   be False or None
@@ -264,8 +148,8 @@ that this commit is two revisions ("+2") beyond the "0.11" tag. For released
 software (exactly equal to a known tag), the identifier will only contain the
 stripped tag, e.g. "0.11".
 
-Other styles are available. See details.md in the Versioneer source tree for
-descriptions.
+Other styles are available. See [details.md](details.md) in the Versioneer
+source tree for descriptions.
 
 ## Debugging
 
@@ -275,47 +159,83 @@ version`, which will run the version-lookup code in a verbose mode, and will
 display the full contents of `get_versions()` (including the `error` string,
 which may help identify what went wrong).
 
-## Updating Versioneer
+## Known Limitations
 
-To upgrade your project to a new release of Versioneer, do the following:
+Some situations are known to cause problems for Versioneer. This details the
+most significant ones. More can be found on Github
+[issues page](https://github.com/python-versioneer/python-versioneer/issues).
 
-* install the new Versioneer (`pip install -U versioneer` or equivalent)
-* edit `setup.cfg`, if necessary, to include any new configuration settings
-  indicated by the release notes
-* re-run `versioneer install` in your source tree, to replace
-  `SRC/_version.py`
-* commit any changed files
+### Subprojects
+
+Versioneer has limited support for source trees in which `setup.py` is not in
+the root directory (e.g. `setup.py` and `.git/` are *not* siblings). The are
+two common reasons why `setup.py` might not be in the root:
+
+* Source trees which contain multiple subprojects, such as
+  [Buildbot](https://github.com/buildbot/buildbot), which contains both
+  "master" and "slave" subprojects, each with their own `setup.py`,
+  `setup.cfg`, and `tox.ini`. Projects like these produce multiple PyPI
+  distributions (and upload multiple independently-installable tarballs).
+* Source trees whose main purpose is to contain a C library, but which also
+  provide bindings to Python (and perhaps other languages) in subdirectories.
+
+Versioneer will look for `.git` in parent directories, and most operations
+should get the right version string. However `pip` and `setuptools` have bugs
+and implementation details which frequently cause `pip install .` from a
+subproject directory to fail to find a correct version string (so it usually
+defaults to `0+unknown`).
 
-### Upgrading to 0.15
+`pip install --editable .` should work correctly. `setup.py install` might
+work too.
 
-Starting with this version, Versioneer is configured with a `[versioneer]`
-section in your `setup.cfg` file. Earlier versions required the `setup.py` to
-set attributes on the `versioneer` module immediately after import. The new
-version will refuse to run (raising an exception during import) until you
-have provided the necessary `setup.cfg` section.
+Pip-8.1.1 is known to have this problem, but hopefully it will get fixed in
+some later version.
 
-In addition, the Versioneer package provides an executable named
-`versioneer`, and the installation process is driven by running `versioneer
-install`. In 0.14 and earlier, the executable was named
-`versioneer-installer` and was run without an argument.
+[Bug #38](https://github.com/python-versioneer/python-versioneer/issues/38) is tracking
+this issue. The discussion in
+[PR #61](https://github.com/python-versioneer/python-versioneer/pull/61) describes the
+issue from the Versioneer side in more detail.
+[pip PR#3176](https://github.com/pypa/pip/pull/3176) and
+[pip PR#3615](https://github.com/pypa/pip/pull/3615) contain work to improve
+pip to let Versioneer work correctly.
 
-### Upgrading to 0.14
+Versioneer-0.16 and earlier only looked for a `.git` directory next to the
+`setup.cfg`, so subprojects were completely unsupported with those releases.
 
-0.14 changes the format of the version string. 0.13 and earlier used
-hyphen-separated strings like "0.11-2-g1076c97-dirty". 0.14 and beyond use a
-plus-separated "local version" section strings, with dot-separated
-components, like "0.11+2.g1076c97". PEP440-strict tools did not like the old
-format, but should be ok with the new one.
+### Editable installs with setuptools <= 18.5
 
-### Upgrading from 0.11 to 0.12
+`setup.py develop` and `pip install --editable .` allow you to install a
+project into a virtualenv once, then continue editing the source code (and
+test) without re-installing after every change.
 
-Nothing special.
+"Entry-point scripts" (`setup(entry_points={"console_scripts": ..})`) are a
+convenient way to specify executable scripts that should be installed along
+with the python package.
 
-### Upgrading from 0.10 to 0.11
+These both work as expected when using modern setuptools. When using
+setuptools-18.5 or earlier, however, certain operations will cause
+`pkg_resources.DistributionNotFound` errors when running the entrypoint
+script, which must be resolved by re-installing the package. This happens
+when the install happens with one version, then the egg_info data is
+regenerated while a different version is checked out. Many setup.py commands
+cause egg_info to be rebuilt (including `sdist`, `wheel`, and installing into
+a different virtualenv), so this can be surprising.
 
-You must add a `versioneer.VCS = "git"` to your `setup.py` before re-running
-`setup.py setup_versioneer`. This will enable the use of additional
-version-control systems (SVN, etc) in the future.
+[Bug #83](https://github.com/python-versioneer/python-versioneer/issues/83) describes
+this one, but upgrading to a newer version of setuptools should probably
+resolve it.
+
+
+## Updating Versioneer
+
+To upgrade your project to a new release of Versioneer, do the following:
+
+* install the new Versioneer (`pip install -U versioneer` or equivalent)
+* edit `setup.cfg`, if necessary, to include any new configuration settings
+  indicated by the release notes. See [UPGRADING](./UPGRADING.md) for details.
+* re-run `versioneer install` in your source tree, to replace
+  `SRC/_version.py`
+* commit any changed files
 
 ## Future Directions
 
@@ -330,35 +250,56 @@ installation by editing setup.py . Alternatively, it might go the other
 direction and include code from all supported VCS systems, reducing the
 number of intermediate scripts.
 
+## Similar projects
+
+* [setuptools_scm](https://github.com/pypa/setuptools_scm/) - a non-vendored build-time
+  dependency
+* [minver](https://github.com/jbweston/miniver) - a lightweight reimplementation of
+  versioneer
+* [versioningit](https://github.com/jwodder/versioningit) - a PEP 518-based setuptools
+  plugin
 
 ## License
 
-To make Versioneer easier to embed, all its code is hereby released into the
-public domain. The `_version.py` that it creates is also in the public
-domain.
+To make Versioneer easier to embed, all its code is dedicated to the public
+domain. The `_version.py` that it creates is also in the public domain.
+Specifically, both are released under the Creative Commons "Public Domain
+Dedication" license (CC0-1.0), as described in
+https://creativecommons.org/publicdomain/zero/1.0/ .
+
+[pypi-image]: https://img.shields.io/pypi/v/versioneer.svg
+[pypi-url]: https://pypi.python.org/pypi/versioneer/
+[travis-image]:
+https://img.shields.io/travis/com/python-versioneer/python-versioneer.svg
+[travis-url]: https://travis-ci.com/github/python-versioneer/python-versioneer
 
 """
+# pylint:disable=invalid-name,import-outside-toplevel,missing-function-docstring
+# pylint:disable=missing-class-docstring,too-many-branches,too-many-statements
+# pylint:disable=raise-missing-from,too-many-lines,too-many-locals,import-error
+# pylint:disable=too-few-public-methods,redefined-outer-name,consider-using-with
+# pylint:disable=attribute-defined-outside-init,too-many-arguments
 
-from __future__ import print_function
-try:
-    import configparser
-except ImportError:
-    import ConfigParser as configparser
+import configparser
 import errno
 import json
 import os
 import re
 import subprocess
 import sys
+from typing import Callable, Dict
 
 
 class VersioneerConfig:
-    pass
+    """Container for Versioneer configuration parameters."""
 
 
 def get_root():
-    # we require that all commands are run from the project root, i.e. the
-    # directory that contains setup.py, setup.cfg, and versioneer.py .
+    """Get the project root directory.
+
+    We require that all commands are run from the project root, i.e. the
+    directory that contains setup.py, setup.cfg, and versioneer.py .
+    """
     root = os.path.realpath(os.path.abspath(os.getcwd()))
     setup_py = os.path.join(root, "setup.py")
     versioneer_py = os.path.join(root, "versioneer.py")
@@ -381,90 +322,99 @@ def get_root():
         # module-import table will cache the first one. So we can't use
         # os.path.dirname(__file__), as that will find whichever
         # versioneer.py was first imported, even in later projects.
-        me = os.path.realpath(os.path.abspath(__file__))
-        if os.path.splitext(me)[0] != os.path.splitext(versioneer_py)[0]:
+        my_path = os.path.realpath(os.path.abspath(__file__))
+        me_dir = os.path.normcase(os.path.splitext(my_path)[0])
+        vsr_dir = os.path.normcase(os.path.splitext(versioneer_py)[0])
+        if me_dir != vsr_dir:
             print("Warning: build in %s is using versioneer.py from %s"
-                  % (os.path.dirname(me), versioneer_py))
+                  % (os.path.dirname(my_path), versioneer_py))
     except NameError:
         pass
     return root
 
 
 def get_config_from_root(root):
-    # This might raise EnvironmentError (if setup.cfg is missing), or
+    """Read the project setup.cfg file to determine Versioneer config."""
+    # This might raise OSError (if setup.cfg is missing), or
     # configparser.NoSectionError (if it lacks a [versioneer] section), or
     # configparser.NoOptionError (if it lacks "VCS="). See the docstring at
     # the top of versioneer.py for instructions on writing your setup.cfg .
     setup_cfg = os.path.join(root, "setup.cfg")
-    parser = configparser.SafeConfigParser()
-    with open(setup_cfg, "r") as f:
-        parser.readfp(f)
+    parser = configparser.ConfigParser()
+    with open(setup_cfg, "r") as cfg_file:
+        parser.read_file(cfg_file)
     VCS = parser.get("versioneer", "VCS")  # mandatory
 
-    def get(parser, name):
-        if parser.has_option("versioneer", name):
-            return parser.get("versioneer", name)
-        return None
+    # Dict-like interface for non-mandatory entries
+    section = parser["versioneer"]
+
     cfg = VersioneerConfig()
     cfg.VCS = VCS
-    cfg.style = get(parser, "style") or ""
-    cfg.versionfile_source = get(parser, "versionfile_source")
-    cfg.versionfile_build = get(parser, "versionfile_build")
-    cfg.tag_prefix = get(parser, "tag_prefix")
-    cfg.parentdir_prefix = get(parser, "parentdir_prefix")
-    cfg.verbose = get(parser, "verbose")
+    cfg.style = section.get("style", "")
+    cfg.versionfile_source = section.get("versionfile_source")
+    cfg.versionfile_build = section.get("versionfile_build")
+    cfg.tag_prefix = section.get("tag_prefix")
+    if cfg.tag_prefix in ("''", '""'):
+        cfg.tag_prefix = ""
+    cfg.parentdir_prefix = section.get("parentdir_prefix")
+    cfg.verbose = section.get("verbose")
     return cfg
 
 
 class NotThisMethod(Exception):
-    pass
+    """Exception raised if a method is not valid for the current scenario."""
+
 
 # these dictionaries contain VCS-specific tools
-LONG_VERSION_PY = {}
-HANDLERS = {}
+LONG_VERSION_PY: Dict[str, str] = {}
+HANDLERS: Dict[str, Dict[str, Callable]] = {}
 
 
 def register_vcs_handler(vcs, method):  # decorator
+    """Create decorator to mark a method as the handler of a VCS."""
     def decorate(f):
-        if vcs not in HANDLERS:
-            HANDLERS[vcs] = {}
-        HANDLERS[vcs][method] = f
+        """Store f in HANDLERS[vcs][method]."""
+        HANDLERS.setdefault(vcs, {})[method] = f
         return f
     return decorate
 
 
-def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False):
+def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False,
+                env=None):
+    """Call the given command(s)."""
     assert isinstance(commands, list)
-    p = None
-    for c in commands:
+    process = None
+    for command in commands:
         try:
-            dispcmd = str([c] + args)
+            dispcmd = str([command] + args)
             # remember shell=False, so use git.cmd on windows, not just git
-            p = subprocess.Popen([c] + args, cwd=cwd, stdout=subprocess.PIPE,
-                                 stderr=(subprocess.PIPE if hide_stderr
-                                         else None))
+            process = subprocess.Popen([command] + args, cwd=cwd, env=env,
+                                       stdout=subprocess.PIPE,
+                                       stderr=(subprocess.PIPE if hide_stderr
+                                               else None))
             break
-        except EnvironmentError:
+        except OSError:
             e = sys.exc_info()[1]
             if e.errno == errno.ENOENT:
                 continue
             if verbose:
                 print("unable to run %s" % dispcmd)
                 print(e)
-            return None
+            return None, None
     else:
         if verbose:
             print("unable to find command, tried %s" % (commands,))
-        return None
-    stdout = p.communicate()[0].strip()
-    if sys.version_info[0] >= 3:
-        stdout = stdout.decode()
-    if p.returncode != 0:
+        return None, None
+    stdout = process.communicate()[0].strip().decode()
+    if process.returncode != 0:
         if verbose:
             print("unable to run %s (error)" % dispcmd)
-        return None
-    return stdout
-LONG_VERSION_PY['git'] = '''
+            print("stdout was %s" % stdout)
+        return None, process.returncode
+    return stdout, process.returncode
+
+
+LONG_VERSION_PY['git'] = r'''
 # This file helps to compute a version number in source trees obtained from
 # git-archive tarball (such as those provided by githubs download-from-tag
 # feature). Distribution tarballs (built by setup.py sdist) and build
@@ -472,31 +422,37 @@ LONG_VERSION_PY['git'] = '''
 # that just contains the computed version number.
 
 # This file is released into the public domain. Generated by
-# versioneer-0.15 (https://github.com/warner/python-versioneer)
+# versioneer-0.21 (https://github.com/python-versioneer/python-versioneer)
+
+"""Git implementation of _version.py."""
 
 import errno
 import os
 import re
 import subprocess
 import sys
+from typing import Callable, Dict
 
 
 def get_keywords():
+    """Get the keywords needed to look up the version information."""
     # these strings will be replaced by git during git-archive.
     # setup.py/versioneer.py will grep for the variable names, so they must
     # each be defined on a line of their own. _version.py will just call
     # get_keywords().
     git_refnames = "%(DOLLAR)sFormat:%%d%(DOLLAR)s"
     git_full = "%(DOLLAR)sFormat:%%H%(DOLLAR)s"
-    keywords = {"refnames": git_refnames, "full": git_full}
+    git_date = "%(DOLLAR)sFormat:%%ci%(DOLLAR)s"
+    keywords = {"refnames": git_refnames, "full": git_full, "date": git_date}
     return keywords
 
 
 class VersioneerConfig:
-    pass
+    """Container for Versioneer configuration parameters."""
 
 
 def get_config():
+    """Create, populate and return the VersioneerConfig() object."""
     # these strings are filled in when 'setup.py versioneer' creates
     # _version.py
     cfg = VersioneerConfig()
@@ -510,15 +466,17 @@ def get_config():
 
 
 class NotThisMethod(Exception):
-    pass
+    """Exception raised if a method is not valid for the current scenario."""
 
 
-LONG_VERSION_PY = {}
-HANDLERS = {}
+LONG_VERSION_PY: Dict[str, str] = {}
+HANDLERS: Dict[str, Dict[str, Callable]] = {}
 
 
 def register_vcs_handler(vcs, method):  # decorator
+    """Create decorator to mark a method as the handler of a VCS."""
     def decorate(f):
+        """Store f in HANDLERS[vcs][method]."""
         if vcs not in HANDLERS:
             HANDLERS[vcs] = {}
         HANDLERS[vcs][method] = f
@@ -526,91 +484,121 @@ def register_vcs_handler(vcs, method):  # decorator
     return decorate
 
 
-def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False):
+def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False,
+                env=None):
+    """Call the given command(s)."""
     assert isinstance(commands, list)
-    p = None
-    for c in commands:
+    process = None
+    for command in commands:
         try:
-            dispcmd = str([c] + args)
+            dispcmd = str([command] + args)
             # remember shell=False, so use git.cmd on windows, not just git
-            p = subprocess.Popen([c] + args, cwd=cwd, stdout=subprocess.PIPE,
-                                 stderr=(subprocess.PIPE if hide_stderr
-                                         else None))
+            process = subprocess.Popen([command] + args, cwd=cwd, env=env,
+                                       stdout=subprocess.PIPE,
+                                       stderr=(subprocess.PIPE if hide_stderr
+                                               else None))
             break
-        except EnvironmentError:
+        except OSError:
             e = sys.exc_info()[1]
             if e.errno == errno.ENOENT:
                 continue
             if verbose:
                 print("unable to run %%s" %% dispcmd)
                 print(e)
-            return None
+            return None, None
     else:
         if verbose:
             print("unable to find command, tried %%s" %% (commands,))
-        return None
-    stdout = p.communicate()[0].strip()
-    if sys.version_info[0] >= 3:
-        stdout = stdout.decode()
-    if p.returncode != 0:
+        return None, None
+    stdout = process.communicate()[0].strip().decode()
+    if process.returncode != 0:
         if verbose:
             print("unable to run %%s (error)" %% dispcmd)
-        return None
-    return stdout
+            print("stdout was %%s" %% stdout)
+        return None, process.returncode
+    return stdout, process.returncode
 
 
 def versions_from_parentdir(parentdir_prefix, root, verbose):
-    # Source tarballs conventionally unpack into a directory that includes
-    # both the project name and a version string.
-    dirname = os.path.basename(root)
-    if not dirname.startswith(parentdir_prefix):
-        if verbose:
-            print("guessing rootdir is '%%s', but '%%s' doesn't start with "
-                  "prefix '%%s'" %% (root, dirname, parentdir_prefix))
-        raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
-    return {"version": dirname[len(parentdir_prefix):],
-            "full-revisionid": None,
-            "dirty": False, "error": None}
+    """Try to determine the version from the parent directory name.
+
+    Source tarballs conventionally unpack into a directory that includes both
+    the project name and a version string. We will also support searching up
+    two directory levels for an appropriately named parent directory
+    """
+    rootdirs = []
+
+    for _ in range(3):
+        dirname = os.path.basename(root)
+        if dirname.startswith(parentdir_prefix):
+            return {"version": dirname[len(parentdir_prefix):],
+                    "full-revisionid": None,
+                    "dirty": False, "error": None, "date": None}
+        rootdirs.append(root)
+        root = os.path.dirname(root)  # up a level
+
+    if verbose:
+        print("Tried directories %%s but none started with prefix %%s" %%
+              (str(rootdirs), parentdir_prefix))
+    raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
 
 
 @register_vcs_handler("git", "get_keywords")
 def git_get_keywords(versionfile_abs):
+    """Extract version information from the given file."""
     # the code embedded in _version.py can just fetch the value of these
     # keywords. When used from setup.py, we don't want to import _version.py,
     # so we do it with a regexp instead. This function is not used from
     # _version.py.
     keywords = {}
     try:
-        f = open(versionfile_abs, "r")
-        for line in f.readlines():
-            if line.strip().startswith("git_refnames ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["refnames"] = mo.group(1)
-            if line.strip().startswith("git_full ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["full"] = mo.group(1)
-        f.close()
-    except EnvironmentError:
+        with open(versionfile_abs, "r") as fobj:
+            for line in fobj:
+                if line.strip().startswith("git_refnames ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["refnames"] = mo.group(1)
+                if line.strip().startswith("git_full ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["full"] = mo.group(1)
+                if line.strip().startswith("git_date ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["date"] = mo.group(1)
+    except OSError:
         pass
     return keywords
 
 
 @register_vcs_handler("git", "keywords")
 def git_versions_from_keywords(keywords, tag_prefix, verbose):
-    if not keywords:
-        raise NotThisMethod("no keywords at all, weird")
+    """Get version information from git keywords."""
+    if "refnames" not in keywords:
+        raise NotThisMethod("Short version file found")
+    date = keywords.get("date")
+    if date is not None:
+        # Use only the last line.  Previous lines may contain GPG signature
+        # information.
+        date = date.splitlines()[-1]
+
+        # git-2.2.0 added "%%cI", which expands to an ISO-8601 -compliant
+        # datestamp. However we prefer "%%ci" (which expands to an "ISO-8601
+        # -like" string, which we must then edit to make compliant), because
+        # it's been around since git-1.5.3, and it's too difficult to
+        # discover which version we're using, or to work around using an
+        # older one.
+        date = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
     refnames = keywords["refnames"].strip()
     if refnames.startswith("$Format"):
         if verbose:
             print("keywords are unexpanded, not using")
         raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
-    refs = set([r.strip() for r in refnames.strip("()").split(",")])
+    refs = {r.strip() for r in refnames.strip("()").split(",")}
     # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
     # just "foo-1.0". If we see a "tag: " prefix, prefer those.
     TAG = "tag: "
-    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
+    tags = {r[len(TAG):] for r in refs if r.startswith(TAG)}
     if not tags:
         # Either we're using git < 1.8.3, or there really are no tags. We use
         # a heuristic: assume all version tags have a digit. The old git %%d
@@ -619,54 +607,67 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         # between branches and tags. By ignoring refnames without digits, we
         # filter out many common branch names like "release" and
         # "stabilization", as well as "HEAD" and "master".
-        tags = set([r for r in refs if re.search(r'\d', r)])
+        tags = {r for r in refs if re.search(r'\d', r)}
         if verbose:
-            print("discarding '%%s', no digits" %% ",".join(refs-tags))
+            print("discarding '%%s', no digits" %% ",".join(refs - tags))
     if verbose:
         print("likely tags: %%s" %% ",".join(sorted(tags)))
     for ref in sorted(tags):
         # sorting will prefer e.g. "2.0" over "2.0rc1"
         if ref.startswith(tag_prefix):
             r = ref[len(tag_prefix):]
+            # Filter out refs that exactly match prefix or that don't start
+            # with a number once the prefix is stripped (mostly a concern
+            # when prefix is '')
+            if not re.match(r'\d', r):
+                continue
             if verbose:
                 print("picking %%s" %% r)
             return {"version": r,
                     "full-revisionid": keywords["full"].strip(),
-                    "dirty": False, "error": None
-                    }
+                    "dirty": False, "error": None,
+                    "date": date}
     # no suitable tags, so version is "0+unknown", but full hex is still there
     if verbose:
         print("no suitable tags, using unknown + full revision id")
     return {"version": "0+unknown",
             "full-revisionid": keywords["full"].strip(),
-            "dirty": False, "error": "no suitable tags"}
+            "dirty": False, "error": "no suitable tags", "date": None}
 
 
 @register_vcs_handler("git", "pieces_from_vcs")
-def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
-    # this runs 'git' from the root of the source tree. This only gets called
-    # if the git-archive 'subst' keywords were *not* expanded, and
-    # _version.py hasn't already been rewritten with a short version string,
-    # meaning we're inside a checked out source tree.
-
-    if not os.path.exists(os.path.join(root, ".git")):
-        if verbose:
-            print("no .git in %%s" %% root)
-        raise NotThisMethod("no .git directory")
+def git_pieces_from_vcs(tag_prefix, root, verbose, runner=run_command):
+    """Get version from 'git describe' in the root of the source tree.
 
+    This only gets called if the git-archive 'subst' keywords were *not*
+    expanded, and _version.py hasn't already been rewritten with a short
+    version string, meaning we're inside a checked out source tree.
+    """
     GITS = ["git"]
+    TAG_PREFIX_REGEX = "*"
     if sys.platform == "win32":
         GITS = ["git.cmd", "git.exe"]
-    # if there is a tag, this yields TAG-NUM-gHEX[-dirty]
-    # if there are no tags, this yields HEX[-dirty] (no NUM)
-    describe_out = run_command(GITS, ["describe", "--tags", "--dirty",
-                                      "--always", "--long"],
-                               cwd=root)
+        TAG_PREFIX_REGEX = r"\*"
+
+    _, rc = runner(GITS, ["rev-parse", "--git-dir"], cwd=root,
+                   hide_stderr=True)
+    if rc != 0:
+        if verbose:
+            print("Directory %%s not under git control" %% root)
+        raise NotThisMethod("'git rev-parse --git-dir' returned error")
+
+    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
+    # if there isn't one, this yields HEX[-dirty] (no NUM)
+    describe_out, rc = runner(GITS, ["describe", "--tags", "--dirty",
+                                     "--always", "--long",
+                                     "--match",
+                                     "%%s%%s" %% (tag_prefix, TAG_PREFIX_REGEX)],
+                              cwd=root)
     # --long was added in git-1.5.5
     if describe_out is None:
         raise NotThisMethod("'git describe' failed")
     describe_out = describe_out.strip()
-    full_out = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
+    full_out, rc = runner(GITS, ["rev-parse", "HEAD"], cwd=root)
     if full_out is None:
         raise NotThisMethod("'git rev-parse' failed")
     full_out = full_out.strip()
@@ -676,6 +677,39 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     pieces["short"] = full_out[:7]  # maybe improved later
     pieces["error"] = None
 
+    branch_name, rc = runner(GITS, ["rev-parse", "--abbrev-ref", "HEAD"],
+                             cwd=root)
+    # --abbrev-ref was added in git-1.6.3
+    if rc != 0 or branch_name is None:
+        raise NotThisMethod("'git rev-parse --abbrev-ref' returned error")
+    branch_name = branch_name.strip()
+
+    if branch_name == "HEAD":
+        # If we aren't exactly on a branch, pick a branch which represents
+        # the current commit. If all else fails, we are on a branchless
+        # commit.
+        branches, rc = runner(GITS, ["branch", "--contains"], cwd=root)
+        # --contains was added in git-1.5.4
+        if rc != 0 or branches is None:
+            raise NotThisMethod("'git branch --contains' returned error")
+        branches = branches.split("\n")
+
+        # Remove the first line if we're running detached
+        if "(" in branches[0]:
+            branches.pop(0)
+
+        # Strip off the leading "* " from the list of branches.
+        branches = [branch[2:] for branch in branches]
+        if "master" in branches:
+            branch_name = "master"
+        elif not branches:
+            branch_name = None
+        else:
+            # Pick the first branch that is returned. Good or bad.
+            branch_name = branches[0]
+
+    pieces["branch"] = branch_name
+
     # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
     # TAG might have hyphens.
     git_describe = describe_out
@@ -692,7 +726,7 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
         # TAG-NUM-gHEX
         mo = re.search(r'^(.+)-(\d+)-g([0-9a-f]+)$', git_describe)
         if not mo:
-            # unparseable. Maybe git-describe is misbehaving?
+            # unparsable. Maybe git-describe is misbehaving?
             pieces["error"] = ("unable to parse git-describe output: '%%s'"
                                %% describe_out)
             return pieces
@@ -717,27 +751,35 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     else:
         # HEX: no tags
         pieces["closest-tag"] = None
-        count_out = run_command(GITS, ["rev-list", "HEAD", "--count"],
-                                cwd=root)
+        count_out, rc = runner(GITS, ["rev-list", "HEAD", "--count"], cwd=root)
         pieces["distance"] = int(count_out)  # total number of commits
 
+    # commit date: see ISO-8601 comment in git_versions_from_keywords()
+    date = runner(GITS, ["show", "-s", "--format=%%ci", "HEAD"], cwd=root)[0].strip()
+    # Use only the last line.  Previous lines may contain GPG signature
+    # information.
+    date = date.splitlines()[-1]
+    pieces["date"] = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
+
     return pieces
 
 
 def plus_or_dot(pieces):
+    """Return a + if we don't already have one, else return a ."""
     if "+" in pieces.get("closest-tag", ""):
         return "."
     return "+"
 
 
 def render_pep440(pieces):
-    # now build up version string, with post-release "local version
-    # identifier". Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
-    # get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
+    """Build up version string, with post-release "local version identifier".
 
-    # exceptions:
-    # 1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
+    get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
 
+    Exceptions:
+    1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -754,31 +796,80 @@ def render_pep440(pieces):
     return rendered
 
 
-def render_pep440_pre(pieces):
-    # TAG[.post.devDISTANCE] . No -dirty
+def render_pep440_branch(pieces):
+    """TAG[[.dev0]+DISTANCE.gHEX[.dirty]] .
 
-    # exceptions:
-    # 1: no tags. 0.post.devDISTANCE
+    The ".dev0" means not master branch. Note that .dev0 sorts backwards
+    (a feature branch will appear "older" than the master branch).
 
+    Exceptions:
+    1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "%%d.g%%s" %% (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0"
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+untagged.%%d.g%%s" %% (pieces["distance"],
+                                          pieces["short"])
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
+def pep440_split_post(ver):
+    """Split pep440 version string at the post-release segment.
+
+    Returns the release segments before the post-release and the
+    post-release version number (or -1 if no post-release segment is present).
+    """
+    vc = str.split(ver, ".post")
+    return vc[0], int(vc[1] or 0) if len(vc) == 2 else None
+
+
+def render_pep440_pre(pieces):
+    """TAG[.postN.devDISTANCE] -- No -dirty.
+
+    Exceptions:
+    1: no tags. 0.post0.devDISTANCE
+    """
+    if pieces["closest-tag"]:
         if pieces["distance"]:
-            rendered += ".post.dev%%d" %% pieces["distance"]
+            # update the post release segment
+            tag_version, post_version = pep440_split_post(pieces["closest-tag"])
+            rendered = tag_version
+            if post_version is not None:
+                rendered += ".post%%d.dev%%d" %% (post_version+1, pieces["distance"])
+            else:
+                rendered += ".post0.dev%%d" %% (pieces["distance"])
+        else:
+            # no commits, use the tag as the version
+            rendered = pieces["closest-tag"]
     else:
         # exception #1
-        rendered = "0.post.dev%%d" %% pieces["distance"]
+        rendered = "0.post0.dev%%d" %% pieces["distance"]
     return rendered
 
 
 def render_pep440_post(pieces):
-    # TAG[.postDISTANCE[.dev0]+gHEX] . The ".dev0" means dirty. Note that
-    # .dev0 sorts backwards (a dirty tree will appear "older" than the
-    # corresponding clean one), but you shouldn't be releasing software with
-    # -dirty anyways.
+    """TAG[.postDISTANCE[.dev0]+gHEX] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty. Note that .dev0 sorts backwards
+    (a dirty tree will appear "older" than the corresponding clean one),
+    but you shouldn't be releasing software with -dirty anyways.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -796,12 +887,43 @@ def render_pep440_post(pieces):
     return rendered
 
 
+def render_pep440_post_branch(pieces):
+    """TAG[.postDISTANCE[.dev0]+gHEX[.dirty]] .
+
+    The ".dev0" means not master branch.
+
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]+gHEX[.dirty]
+    """
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".post%%d" %% pieces["distance"]
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "g%%s" %% pieces["short"]
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0.post%%d" %% pieces["distance"]
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+g%%s" %% pieces["short"]
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
 def render_pep440_old(pieces):
-    # TAG[.postDISTANCE[.dev0]] . The ".dev0" means dirty.
+    """TAG[.postDISTANCE[.dev0]] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -817,12 +939,13 @@ def render_pep440_old(pieces):
 
 
 def render_git_describe(pieces):
-    # TAG[-DISTANCE-gHEX][-dirty], like 'git describe --tags --dirty
-    # --always'
+    """TAG[-DISTANCE-gHEX][-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always'.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"]:
@@ -836,12 +959,14 @@ def render_git_describe(pieces):
 
 
 def render_git_describe_long(pieces):
-    # TAG-DISTANCE-gHEX[-dirty], like 'git describe --tags --dirty
-    # --always -long'. The distance/hash is unconditional.
+    """TAG-DISTANCE-gHEX[-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always -long'.
+    The distance/hash is unconditional.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         rendered += "-%%d-g%%s" %% (pieces["distance"], pieces["short"])
@@ -854,21 +979,27 @@ def render_git_describe_long(pieces):
 
 
 def render(pieces, style):
+    """Render the given version pieces into the requested style."""
     if pieces["error"]:
         return {"version": "unknown",
                 "full-revisionid": pieces.get("long"),
                 "dirty": None,
-                "error": pieces["error"]}
+                "error": pieces["error"],
+                "date": None}
 
     if not style or style == "default":
         style = "pep440"  # the default
 
     if style == "pep440":
         rendered = render_pep440(pieces)
+    elif style == "pep440-branch":
+        rendered = render_pep440_branch(pieces)
     elif style == "pep440-pre":
         rendered = render_pep440_pre(pieces)
     elif style == "pep440-post":
         rendered = render_pep440_post(pieces)
+    elif style == "pep440-post-branch":
+        rendered = render_pep440_post_branch(pieces)
     elif style == "pep440-old":
         rendered = render_pep440_old(pieces)
     elif style == "git-describe":
@@ -879,10 +1010,12 @@ def render(pieces, style):
         raise ValueError("unknown style '%%s'" %% style)
 
     return {"version": rendered, "full-revisionid": pieces["long"],
-            "dirty": pieces["dirty"], "error": None}
+            "dirty": pieces["dirty"], "error": None,
+            "date": pieces.get("date")}
 
 
 def get_versions():
+    """Get version information or return default if unable to do so."""
     # I am in _version.py, which lives at ROOT/VERSIONFILE_SOURCE. If we have
     # __file__, we can work backwards from there to the root. Some
     # py2exe/bbfreeze/non-CPython implementations don't do __file__, in which
@@ -902,12 +1035,13 @@ def get_versions():
         # versionfile_source is the relative path from the top of the source
         # tree (where the .git directory might live) to this file. Invert
         # this to find the root from __file__.
-        for i in cfg.versionfile_source.split('/'):
+        for _ in cfg.versionfile_source.split('/'):
             root = os.path.dirname(root)
     except NameError:
         return {"version": "0+unknown", "full-revisionid": None,
                 "dirty": None,
-                "error": "unable to find root of source tree"}
+                "error": "unable to find root of source tree",
+                "date": None}
 
     try:
         pieces = git_pieces_from_vcs(cfg.tag_prefix, root, verbose)
@@ -923,48 +1057,66 @@ def get_versions():
 
     return {"version": "0+unknown", "full-revisionid": None,
             "dirty": None,
-            "error": "unable to compute version"}
+            "error": "unable to compute version", "date": None}
 '''
 
 
 @register_vcs_handler("git", "get_keywords")
 def git_get_keywords(versionfile_abs):
+    """Extract version information from the given file."""
     # the code embedded in _version.py can just fetch the value of these
     # keywords. When used from setup.py, we don't want to import _version.py,
     # so we do it with a regexp instead. This function is not used from
     # _version.py.
     keywords = {}
     try:
-        f = open(versionfile_abs, "r")
-        for line in f.readlines():
-            if line.strip().startswith("git_refnames ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["refnames"] = mo.group(1)
-            if line.strip().startswith("git_full ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["full"] = mo.group(1)
-        f.close()
-    except EnvironmentError:
+        with open(versionfile_abs, "r") as fobj:
+            for line in fobj:
+                if line.strip().startswith("git_refnames ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["refnames"] = mo.group(1)
+                if line.strip().startswith("git_full ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["full"] = mo.group(1)
+                if line.strip().startswith("git_date ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["date"] = mo.group(1)
+    except OSError:
         pass
     return keywords
 
 
 @register_vcs_handler("git", "keywords")
 def git_versions_from_keywords(keywords, tag_prefix, verbose):
-    if not keywords:
-        raise NotThisMethod("no keywords at all, weird")
+    """Get version information from git keywords."""
+    if "refnames" not in keywords:
+        raise NotThisMethod("Short version file found")
+    date = keywords.get("date")
+    if date is not None:
+        # Use only the last line.  Previous lines may contain GPG signature
+        # information.
+        date = date.splitlines()[-1]
+
+        # git-2.2.0 added "%cI", which expands to an ISO-8601 -compliant
+        # datestamp. However we prefer "%ci" (which expands to an "ISO-8601
+        # -like" string, which we must then edit to make compliant), because
+        # it's been around since git-1.5.3, and it's too difficult to
+        # discover which version we're using, or to work around using an
+        # older one.
+        date = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
     refnames = keywords["refnames"].strip()
     if refnames.startswith("$Format"):
         if verbose:
             print("keywords are unexpanded, not using")
         raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
-    refs = set([r.strip() for r in refnames.strip("()").split(",")])
+    refs = {r.strip() for r in refnames.strip("()").split(",")}
     # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
     # just "foo-1.0". If we see a "tag: " prefix, prefer those.
     TAG = "tag: "
-    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
+    tags = {r[len(TAG):] for r in refs if r.startswith(TAG)}
     if not tags:
         # Either we're using git < 1.8.3, or there really are no tags. We use
         # a heuristic: assume all version tags have a digit. The old git %d
@@ -973,54 +1125,67 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         # between branches and tags. By ignoring refnames without digits, we
         # filter out many common branch names like "release" and
         # "stabilization", as well as "HEAD" and "master".
-        tags = set([r for r in refs if re.search(r'\d', r)])
+        tags = {r for r in refs if re.search(r'\d', r)}
         if verbose:
-            print("discarding '%s', no digits" % ",".join(refs-tags))
+            print("discarding '%s', no digits" % ",".join(refs - tags))
     if verbose:
         print("likely tags: %s" % ",".join(sorted(tags)))
     for ref in sorted(tags):
         # sorting will prefer e.g. "2.0" over "2.0rc1"
         if ref.startswith(tag_prefix):
             r = ref[len(tag_prefix):]
+            # Filter out refs that exactly match prefix or that don't start
+            # with a number once the prefix is stripped (mostly a concern
+            # when prefix is '')
+            if not re.match(r'\d', r):
+                continue
             if verbose:
                 print("picking %s" % r)
             return {"version": r,
                     "full-revisionid": keywords["full"].strip(),
-                    "dirty": False, "error": None
-                    }
+                    "dirty": False, "error": None,
+                    "date": date}
     # no suitable tags, so version is "0+unknown", but full hex is still there
     if verbose:
         print("no suitable tags, using unknown + full revision id")
     return {"version": "0+unknown",
             "full-revisionid": keywords["full"].strip(),
-            "dirty": False, "error": "no suitable tags"}
+            "dirty": False, "error": "no suitable tags", "date": None}
 
 
 @register_vcs_handler("git", "pieces_from_vcs")
-def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
-    # this runs 'git' from the root of the source tree. This only gets called
-    # if the git-archive 'subst' keywords were *not* expanded, and
-    # _version.py hasn't already been rewritten with a short version string,
-    # meaning we're inside a checked out source tree.
-
-    if not os.path.exists(os.path.join(root, ".git")):
-        if verbose:
-            print("no .git in %s" % root)
-        raise NotThisMethod("no .git directory")
+def git_pieces_from_vcs(tag_prefix, root, verbose, runner=run_command):
+    """Get version from 'git describe' in the root of the source tree.
 
+    This only gets called if the git-archive 'subst' keywords were *not*
+    expanded, and _version.py hasn't already been rewritten with a short
+    version string, meaning we're inside a checked out source tree.
+    """
     GITS = ["git"]
+    TAG_PREFIX_REGEX = "*"
     if sys.platform == "win32":
         GITS = ["git.cmd", "git.exe"]
-    # if there is a tag, this yields TAG-NUM-gHEX[-dirty]
-    # if there are no tags, this yields HEX[-dirty] (no NUM)
-    describe_out = run_command(GITS, ["describe", "--tags", "--dirty",
-                                      "--always", "--long"],
-                               cwd=root)
+        TAG_PREFIX_REGEX = r"\*"
+
+    _, rc = runner(GITS, ["rev-parse", "--git-dir"], cwd=root,
+                   hide_stderr=True)
+    if rc != 0:
+        if verbose:
+            print("Directory %s not under git control" % root)
+        raise NotThisMethod("'git rev-parse --git-dir' returned error")
+
+    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
+    # if there isn't one, this yields HEX[-dirty] (no NUM)
+    describe_out, rc = runner(GITS, ["describe", "--tags", "--dirty",
+                                     "--always", "--long",
+                                     "--match",
+                                     "%s%s" % (tag_prefix, TAG_PREFIX_REGEX)],
+                              cwd=root)
     # --long was added in git-1.5.5
     if describe_out is None:
         raise NotThisMethod("'git describe' failed")
     describe_out = describe_out.strip()
-    full_out = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
+    full_out, rc = runner(GITS, ["rev-parse", "HEAD"], cwd=root)
     if full_out is None:
         raise NotThisMethod("'git rev-parse' failed")
     full_out = full_out.strip()
@@ -1030,6 +1195,39 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     pieces["short"] = full_out[:7]  # maybe improved later
     pieces["error"] = None
 
+    branch_name, rc = runner(GITS, ["rev-parse", "--abbrev-ref", "HEAD"],
+                             cwd=root)
+    # --abbrev-ref was added in git-1.6.3
+    if rc != 0 or branch_name is None:
+        raise NotThisMethod("'git rev-parse --abbrev-ref' returned error")
+    branch_name = branch_name.strip()
+
+    if branch_name == "HEAD":
+        # If we aren't exactly on a branch, pick a branch which represents
+        # the current commit. If all else fails, we are on a branchless
+        # commit.
+        branches, rc = runner(GITS, ["branch", "--contains"], cwd=root)
+        # --contains was added in git-1.5.4
+        if rc != 0 or branches is None:
+            raise NotThisMethod("'git branch --contains' returned error")
+        branches = branches.split("\n")
+
+        # Remove the first line if we're running detached
+        if "(" in branches[0]:
+            branches.pop(0)
+
+        # Strip off the leading "* " from the list of branches.
+        branches = [branch[2:] for branch in branches]
+        if "master" in branches:
+            branch_name = "master"
+        elif not branches:
+            branch_name = None
+        else:
+            # Pick the first branch that is returned. Good or bad.
+            branch_name = branches[0]
+
+    pieces["branch"] = branch_name
+
     # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
     # TAG might have hyphens.
     git_describe = describe_out
@@ -1046,7 +1244,7 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
         # TAG-NUM-gHEX
         mo = re.search(r'^(.+)-(\d+)-g([0-9a-f]+)$', git_describe)
         if not mo:
-            # unparseable. Maybe git-describe is misbehaving?
+            # unparsable. Maybe git-describe is misbehaving?
             pieces["error"] = ("unable to parse git-describe output: '%s'"
                                % describe_out)
             return pieces
@@ -1071,14 +1269,25 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     else:
         # HEX: no tags
         pieces["closest-tag"] = None
-        count_out = run_command(GITS, ["rev-list", "HEAD", "--count"],
-                                cwd=root)
+        count_out, rc = runner(GITS, ["rev-list", "HEAD", "--count"], cwd=root)
         pieces["distance"] = int(count_out)  # total number of commits
 
+    # commit date: see ISO-8601 comment in git_versions_from_keywords()
+    date = runner(GITS, ["show", "-s", "--format=%ci", "HEAD"], cwd=root)[0].strip()
+    # Use only the last line.  Previous lines may contain GPG signature
+    # information.
+    date = date.splitlines()[-1]
+    pieces["date"] = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
+
     return pieces
 
 
 def do_vcs_install(manifest_in, versionfile_source, ipy):
+    """Git-specific installation logic for Versioneer.
+
+    For Git, this means creating/changing .gitattributes to mark _version.py
+    for export-subst keyword substitution.
+    """
     GITS = ["git"]
     if sys.platform == "win32":
         GITS = ["git.cmd", "git.exe"]
@@ -1086,52 +1295,61 @@ def do_vcs_install(manifest_in, versionfile_source, ipy):
     if ipy:
         files.append(ipy)
     try:
-        me = __file__
-        if me.endswith(".pyc") or me.endswith(".pyo"):
-            me = os.path.splitext(me)[0] + ".py"
-        versioneer_file = os.path.relpath(me)
+        my_path = __file__
+        if my_path.endswith(".pyc") or my_path.endswith(".pyo"):
+            my_path = os.path.splitext(my_path)[0] + ".py"
+        versioneer_file = os.path.relpath(my_path)
     except NameError:
         versioneer_file = "versioneer.py"
     files.append(versioneer_file)
     present = False
     try:
-        f = open(".gitattributes", "r")
-        for line in f.readlines():
-            if line.strip().startswith(versionfile_source):
-                if "export-subst" in line.strip().split()[1:]:
-                    present = True
-        f.close()
-    except EnvironmentError:
+        with open(".gitattributes", "r") as fobj:
+            for line in fobj:
+                if line.strip().startswith(versionfile_source):
+                    if "export-subst" in line.strip().split()[1:]:
+                        present = True
+                        break
+    except OSError:
         pass
     if not present:
-        f = open(".gitattributes", "a+")
-        f.write("%s export-subst\n" % versionfile_source)
-        f.close()
+        with open(".gitattributes", "a+") as fobj:
+            fobj.write(f"{versionfile_source} export-subst\n")
         files.append(".gitattributes")
     run_command(GITS, ["add", "--"] + files)
 
 
 def versions_from_parentdir(parentdir_prefix, root, verbose):
-    # Source tarballs conventionally unpack into a directory that includes
-    # both the project name and a version string.
-    dirname = os.path.basename(root)
-    if not dirname.startswith(parentdir_prefix):
-        if verbose:
-            print("guessing rootdir is '%s', but '%s' doesn't start with "
-                  "prefix '%s'" % (root, dirname, parentdir_prefix))
-        raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
-    return {"version": dirname[len(parentdir_prefix):],
-            "full-revisionid": None,
-            "dirty": False, "error": None}
+    """Try to determine the version from the parent directory name.
+
+    Source tarballs conventionally unpack into a directory that includes both
+    the project name and a version string. We will also support searching up
+    two directory levels for an appropriately named parent directory
+    """
+    rootdirs = []
+
+    for _ in range(3):
+        dirname = os.path.basename(root)
+        if dirname.startswith(parentdir_prefix):
+            return {"version": dirname[len(parentdir_prefix):],
+                    "full-revisionid": None,
+                    "dirty": False, "error": None, "date": None}
+        rootdirs.append(root)
+        root = os.path.dirname(root)  # up a level
+
+    if verbose:
+        print("Tried directories %s but none started with prefix %s" %
+              (str(rootdirs), parentdir_prefix))
+    raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
+
 
 SHORT_VERSION_PY = """
-# This file was generated by 'versioneer.py' (0.15) from
+# This file was generated by 'versioneer.py' (0.21) from
 # revision-control system data, or from the parent directory name of an
 # unpacked source archive. Distribution tarballs contain a pre-generated copy
 # of this file.
 
 import json
-import sys
 
 version_json = '''
 %s
@@ -1144,19 +1362,24 @@ def get_versions():
 
 
 def versions_from_file(filename):
+    """Try to determine the version from _version.py if present."""
     try:
         with open(filename) as f:
             contents = f.read()
-    except EnvironmentError:
+    except OSError:
         raise NotThisMethod("unable to read _version.py")
     mo = re.search(r"version_json = '''\n(.*)'''  # END VERSION_JSON",
                    contents, re.M | re.S)
+    if not mo:
+        mo = re.search(r"version_json = '''\r\n(.*)'''  # END VERSION_JSON",
+                       contents, re.M | re.S)
     if not mo:
         raise NotThisMethod("no version_json in _version.py")
     return json.loads(mo.group(1))
 
 
 def write_to_version_file(filename, versions):
+    """Write the given version number to the given _version.py file."""
     os.unlink(filename)
     contents = json.dumps(versions, sort_keys=True,
                           indent=1, separators=(",", ": "))
@@ -1167,19 +1390,21 @@ def write_to_version_file(filename, versions):
 
 
 def plus_or_dot(pieces):
+    """Return a + if we don't already have one, else return a ."""
     if "+" in pieces.get("closest-tag", ""):
         return "."
     return "+"
 
 
 def render_pep440(pieces):
-    # now build up version string, with post-release "local version
-    # identifier". Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
-    # get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
+    """Build up version string, with post-release "local version identifier".
 
-    # exceptions:
-    # 1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
+    get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty
 
+    Exceptions:
+    1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -1196,31 +1421,80 @@ def render_pep440(pieces):
     return rendered
 
 
-def render_pep440_pre(pieces):
-    # TAG[.post.devDISTANCE] . No -dirty
+def render_pep440_branch(pieces):
+    """TAG[[.dev0]+DISTANCE.gHEX[.dirty]] .
 
-    # exceptions:
-    # 1: no tags. 0.post.devDISTANCE
+    The ".dev0" means not master branch. Note that .dev0 sorts backwards
+    (a feature branch will appear "older" than the master branch).
 
+    Exceptions:
+    1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0"
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+untagged.%d.g%s" % (pieces["distance"],
+                                          pieces["short"])
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
+def pep440_split_post(ver):
+    """Split pep440 version string at the post-release segment.
+
+    Returns the release segments before the post-release and the
+    post-release version number (or -1 if no post-release segment is present).
+    """
+    vc = str.split(ver, ".post")
+    return vc[0], int(vc[1] or 0) if len(vc) == 2 else None
+
+
+def render_pep440_pre(pieces):
+    """TAG[.postN.devDISTANCE] -- No -dirty.
+
+    Exceptions:
+    1: no tags. 0.post0.devDISTANCE
+    """
+    if pieces["closest-tag"]:
         if pieces["distance"]:
-            rendered += ".post.dev%d" % pieces["distance"]
+            # update the post release segment
+            tag_version, post_version = pep440_split_post(pieces["closest-tag"])
+            rendered = tag_version
+            if post_version is not None:
+                rendered += ".post%d.dev%d" % (post_version+1, pieces["distance"])
+            else:
+                rendered += ".post0.dev%d" % (pieces["distance"])
+        else:
+            # no commits, use the tag as the version
+            rendered = pieces["closest-tag"]
     else:
         # exception #1
-        rendered = "0.post.dev%d" % pieces["distance"]
+        rendered = "0.post0.dev%d" % pieces["distance"]
     return rendered
 
 
 def render_pep440_post(pieces):
-    # TAG[.postDISTANCE[.dev0]+gHEX] . The ".dev0" means dirty. Note that
-    # .dev0 sorts backwards (a dirty tree will appear "older" than the
-    # corresponding clean one), but you shouldn't be releasing software with
-    # -dirty anyways.
+    """TAG[.postDISTANCE[.dev0]+gHEX] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty. Note that .dev0 sorts backwards
+    (a dirty tree will appear "older" than the corresponding clean one),
+    but you shouldn't be releasing software with -dirty anyways.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -1238,12 +1512,43 @@ def render_pep440_post(pieces):
     return rendered
 
 
+def render_pep440_post_branch(pieces):
+    """TAG[.postDISTANCE[.dev0]+gHEX[.dirty]] .
+
+    The ".dev0" means not master branch.
+
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]+gHEX[.dirty]
+    """
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".post%d" % pieces["distance"]
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "g%s" % pieces["short"]
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0.post%d" % pieces["distance"]
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+g%s" % pieces["short"]
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
 def render_pep440_old(pieces):
-    # TAG[.postDISTANCE[.dev0]] . The ".dev0" means dirty.
+    """TAG[.postDISTANCE[.dev0]] .
 
-    # exceptions:
-    # 1: no tags. 0.postDISTANCE[.dev0]
+    The ".dev0" means dirty.
 
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"] or pieces["dirty"]:
@@ -1259,12 +1564,13 @@ def render_pep440_old(pieces):
 
 
 def render_git_describe(pieces):
-    # TAG[-DISTANCE-gHEX][-dirty], like 'git describe --tags --dirty
-    # --always'
+    """TAG[-DISTANCE-gHEX][-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always'.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         if pieces["distance"]:
@@ -1278,12 +1584,14 @@ def render_git_describe(pieces):
 
 
 def render_git_describe_long(pieces):
-    # TAG-DISTANCE-gHEX[-dirty], like 'git describe --tags --dirty
-    # --always -long'. The distance/hash is unconditional.
+    """TAG-DISTANCE-gHEX[-dirty].
 
-    # exceptions:
-    # 1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    Like 'git describe --tags --dirty --always -long'.
+    The distance/hash is unconditional.
 
+    Exceptions:
+    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
+    """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
         rendered += "-%d-g%s" % (pieces["distance"], pieces["short"])
@@ -1296,21 +1604,27 @@ def render_git_describe_long(pieces):
 
 
 def render(pieces, style):
+    """Render the given version pieces into the requested style."""
     if pieces["error"]:
         return {"version": "unknown",
                 "full-revisionid": pieces.get("long"),
                 "dirty": None,
-                "error": pieces["error"]}
+                "error": pieces["error"],
+                "date": None}
 
     if not style or style == "default":
         style = "pep440"  # the default
 
     if style == "pep440":
         rendered = render_pep440(pieces)
+    elif style == "pep440-branch":
+        rendered = render_pep440_branch(pieces)
     elif style == "pep440-pre":
         rendered = render_pep440_pre(pieces)
     elif style == "pep440-post":
         rendered = render_pep440_post(pieces)
+    elif style == "pep440-post-branch":
+        rendered = render_pep440_post_branch(pieces)
     elif style == "pep440-old":
         rendered = render_pep440_old(pieces)
     elif style == "git-describe":
@@ -1321,16 +1635,19 @@ def render(pieces, style):
         raise ValueError("unknown style '%s'" % style)
 
     return {"version": rendered, "full-revisionid": pieces["long"],
-            "dirty": pieces["dirty"], "error": None}
+            "dirty": pieces["dirty"], "error": None,
+            "date": pieces.get("date")}
 
 
 class VersioneerBadRootError(Exception):
-    pass
+    """The project root directory is unknown or missing key files."""
 
 
 def get_versions(verbose=False):
-    # returns dict with two keys: 'version' and 'full'
+    """Get the project version from whatever source is available.
 
+    Returns dict with two keys: 'version' and 'full'.
+    """
     if "versioneer" in sys.modules:
         # see the discussion in cmdclass.py:get_cmdclass()
         del sys.modules["versioneer"]
@@ -1398,14 +1715,21 @@ def get_versions(verbose=False):
         print("unable to compute version")
 
     return {"version": "0+unknown", "full-revisionid": None,
-            "dirty": None, "error": "unable to compute version"}
+            "dirty": None, "error": "unable to compute version",
+            "date": None}
 
 
 def get_version():
+    """Get the short version string for this project."""
     return get_versions()["version"]
 
 
-def get_cmdclass():
+def get_cmdclass(cmdclass=None):
+    """Get the custom setuptools/distutils subclasses used by Versioneer.
+
+    If the package uses a different cmdclass (e.g. one from numpy), it
+    should be provide as an argument.
+    """
     if "versioneer" in sys.modules:
         del sys.modules["versioneer"]
         # this fixes the "python setup.py develop" case (also 'install' and
@@ -1419,9 +1743,9 @@ def get_cmdclass():
         # parent is protected against the child's "import versioneer". By
         # removing ourselves from sys.modules here, before the child build
         # happens, we protect the child from the parent's versioneer too.
-        # Also see https://github.com/warner/python-versioneer/issues/52
+        # Also see https://github.com/python-versioneer/python-versioneer/issues/52
 
-    cmds = {}
+    cmds = {} if cmdclass is None else cmdclass.copy()
 
     # we add "version" to both distutils and setuptools
     from distutils.core import Command
@@ -1442,6 +1766,7 @@ def get_cmdclass():
             print("Version: %s" % vers["version"])
             print(" full-revisionid: %s" % vers.get("full-revisionid"))
             print(" dirty: %s" % vers.get("dirty"))
+            print(" date: %s" % vers.get("date"))
             if vers["error"]:
                 print(" error: %s" % vers["error"])
     cmds["version"] = cmd_version
@@ -1455,8 +1780,19 @@ def get_cmdclass():
     #  setuptools/bdist_egg -> distutils/install_lib -> build_py
     #  setuptools/install -> bdist_egg ->..
     #  setuptools/develop -> ?
-
-    from distutils.command.build_py import build_py as _build_py
+    #  pip install:
+    #   copies source tree to a tempdir before running egg_info/etc
+    #   if .git isn't copied too, 'git describe' will fail
+    #   then does setup.py bdist_wheel, or sometimes setup.py install
+    #  setup.py egg_info -> ?
+
+    # we override different "build_py" commands for both environments
+    if 'build_py' in cmds:
+        _build_py = cmds['build_py']
+    elif "setuptools" in sys.modules:
+        from setuptools.command.build_py import build_py as _build_py
+    else:
+        from distutils.command.build_py import build_py as _build_py
 
     class cmd_build_py(_build_py):
         def run(self):
@@ -1473,8 +1809,41 @@ def get_cmdclass():
                 write_to_version_file(target_versionfile, versions)
     cmds["build_py"] = cmd_build_py
 
+    if 'build_ext' in cmds:
+        _build_ext = cmds['build_ext']
+    elif "setuptools" in sys.modules:
+        from setuptools.command.build_ext import build_ext as _build_ext
+    else:
+        from distutils.command.build_ext import build_ext as _build_ext
+
+    class cmd_build_ext(_build_ext):
+        def run(self):
+            root = get_root()
+            cfg = get_config_from_root(root)
+            versions = get_versions()
+            _build_ext.run(self)
+            if self.inplace:
+                # build_ext --inplace will only build extensions in
+                # build/lib<..> dir with no _version.py to write to.
+                # As in place builds will already have a _version.py
+                # in the module dir, we do not need to write one.
+                return
+            # now locate _version.py in the new build/ directory and replace
+            # it with an updated value
+            target_versionfile = os.path.join(self.build_lib,
+                                              cfg.versionfile_build)
+            print("UPDATING %s" % target_versionfile)
+            write_to_version_file(target_versionfile, versions)
+    cmds["build_ext"] = cmd_build_ext
+
     if "cx_Freeze" in sys.modules:  # cx_freeze enabled?
         from cx_Freeze.dist import build_exe as _build_exe
+        # nczeczulin reports that py2exe won't like the pep440-style string
+        # as FILEVERSION, but it can be used for PRODUCTVERSION, e.g.
+        # setup(console=[{
+        #   "version": versioneer.get_version().split("+", 1)[0], # FILEVERSION
+        #   "product_version": versioneer.get_version(),
+        #   ...
 
         class cmd_build_exe(_build_exe):
             def run(self):
@@ -1499,8 +1868,35 @@ def get_cmdclass():
         cmds["build_exe"] = cmd_build_exe
         del cmds["build_py"]
 
+    if 'py2exe' in sys.modules:  # py2exe enabled?
+        from py2exe.distutils_buildexe import py2exe as _py2exe
+
+        class cmd_py2exe(_py2exe):
+            def run(self):
+                root = get_root()
+                cfg = get_config_from_root(root)
+                versions = get_versions()
+                target_versionfile = cfg.versionfile_source
+                print("UPDATING %s" % target_versionfile)
+                write_to_version_file(target_versionfile, versions)
+
+                _py2exe.run(self)
+                os.unlink(target_versionfile)
+                with open(cfg.versionfile_source, "w") as f:
+                    LONG = LONG_VERSION_PY[cfg.VCS]
+                    f.write(LONG %
+                            {"DOLLAR": "$",
+                             "STYLE": cfg.style,
+                             "TAG_PREFIX": cfg.tag_prefix,
+                             "PARENTDIR_PREFIX": cfg.parentdir_prefix,
+                             "VERSIONFILE_SOURCE": cfg.versionfile_source,
+                             })
+        cmds["py2exe"] = cmd_py2exe
+
     # we override different "sdist" commands for both environments
-    if "setuptools" in sys.modules:
+    if 'sdist' in cmds:
+        _sdist = cmds['sdist']
+    elif "setuptools" in sys.modules:
         from setuptools.command.sdist import sdist as _sdist
     else:
         from distutils.command.sdist import sdist as _sdist
@@ -1539,7 +1935,7 @@ a section like:
  style = pep440
  versionfile_source = src/myproject/_version.py
  versionfile_build = myproject/_version.py
- tag_prefix = ""
+ tag_prefix =
  parentdir_prefix = myproject-
 
 You will also need to edit your setup.py to use the results:
@@ -1567,20 +1963,26 @@ SAMPLE_CONFIG = """
 
 """
 
-INIT_PY_SNIPPET = """
+OLD_SNIPPET = """
 from ._version import get_versions
 __version__ = get_versions()['version']
 del get_versions
 """
 
+INIT_PY_SNIPPET = """
+from . import {0}
+__version__ = {0}.get_versions()['version']
+"""
+
 
 def do_setup():
+    """Do main VCS-independent setup function for installing Versioneer."""
     root = get_root()
     try:
         cfg = get_config_from_root(root)
-    except (EnvironmentError, configparser.NoSectionError,
+    except (OSError, configparser.NoSectionError,
             configparser.NoOptionError) as e:
-        if isinstance(e, (EnvironmentError, configparser.NoSectionError)):
+        if isinstance(e, (OSError, configparser.NoSectionError)):
             print("Adding sample versioneer config to setup.cfg",
                   file=sys.stderr)
             with open(os.path.join(root, "setup.cfg"), "a") as f:
@@ -1604,12 +2006,18 @@ def do_setup():
         try:
             with open(ipy, "r") as f:
                 old = f.read()
-        except EnvironmentError:
+        except OSError:
             old = ""
-        if INIT_PY_SNIPPET not in old:
+        module = os.path.splitext(os.path.basename(cfg.versionfile_source))[0]
+        snippet = INIT_PY_SNIPPET.format(module)
+        if OLD_SNIPPET in old:
+            print(" replacing boilerplate in %s" % ipy)
+            with open(ipy, "w") as f:
+                f.write(old.replace(OLD_SNIPPET, snippet))
+        elif snippet not in old:
             print(" appending to %s" % ipy)
             with open(ipy, "a") as f:
-                f.write(INIT_PY_SNIPPET)
+                f.write(snippet)
         else:
             print(" %s unmodified" % ipy)
     else:
@@ -1628,7 +2036,7 @@ def do_setup():
                 if line.startswith("include "):
                     for include in line.split()[1:]:
                         simple_includes.add(include)
-    except EnvironmentError:
+    except OSError:
         pass
     # That doesn't cover everything MANIFEST.in can do
     # (http://docs.python.org/2/distutils/sourcedist.html#commands), so
@@ -1649,13 +2057,14 @@ def do_setup():
         print(" versionfile_source already in MANIFEST.in")
 
     # Make VCS-specific changes. For git, this means creating/changing
-    # .gitattributes to mark _version.py for export-time keyword
+    # .gitattributes to mark _version.py for export-subst keyword
     # substitution.
     do_vcs_install(manifest_in, cfg.versionfile_source, ipy)
     return 0
 
 
 def scan_setup_py():
+    """Validate the contents of setup.py against Versioneer's expectations."""
     found = set()
     setters = False
     errors = 0
@@ -1690,6 +2099,7 @@ def scan_setup_py():
         errors += 1
     return errors
 
+
 if __name__ == "__main__":
     cmd = sys.argv[1]
     if cmd == "setup":
-- 
2.36.1