version.py

# -*- coding: utf-8 -*-
"""
Author: Douglas Creager <dcreager@dcreager.net>
This file is placed into the public domain.
Calculates the current version number.  If possible, this is the
output of “git describe”, modified to conform to the versioning
scheme that setuptools uses.  If “git describe” returns an error
(most likely because we're in an unpacked copy of a release tarball,
rather than in a git working copy), then we fall back on reading the
contents of the RELEASE-VERSION file.
To use this script, simply import it your setup.py file, and use the
results of get_git_version() as your package version:
from version import *
setup(
    version=get_git_version(),
    .
    .
    .
)
This will automatically update the RELEASE-VERSION file, if
necessary.  Note that the RELEASE-VERSION file should *not* be
checked into git; please add it to your top-level .gitignore file.
You'll probably want to distribute the RELEASE-VERSION file in your
sdist tarballs; to do this, just create a MANIFEST.in file that
contains the following line:
  include RELEASE-VERSION
"""

__all__ = ("get_git_version")

from subprocess import Popen, PIPE


def call_git_describe(abbrev=4):
    try:
        p = Popen(['git', 'describe', '--abbrev=%d' % abbrev],
                  stdout=PIPE, stderr=PIPE)
        p.stderr.close()
        line = p.stdout.readlines()[0]
        return line.strip()

    except:
        return None


def read_release_version():
    try:
        f = open("RELEASE-VERSION", "r")

        try:
            version = f.readlines()[0]
            return version.strip()
        finally:
            f.close()

    except:
        return None


def write_release_version(version):
    f = open("RELEASE-VERSION", "w")
    f.write("%s\n" % version)
    f.close()


def get_git_version(abbrev=4):
    # Read in the version that's currently in RELEASE-VERSION.

    release_version = read_release_version()

    # First try to get the current version using “git describe”.

    version = call_git_describe(abbrev)

    # If that doesn't work, fall back on the value that's in
    # RELEASE-VERSION.

    if version is None:
        version = release_version

    # If we still don't have anything, that's an error.

    if version is None:
        raise ValueError("Cannot find the version number!")

    # If the current version is different from what's in the
    # RELEASE-VERSION file, update the file to be current.

    if version != release_version:
        write_release_version(version)

    # Finally, return the current version.

    return version


if __name__ == "__main__":
    print get_git_version()