Produce a setuptools-compatible package version number based on git tags

version.py

"""Calculate the current package version number based on git tags.

If possible, use the output of `git describe` modified to conform to the
versioning scheme that setuptools uses (see PEP 386).  Releases must be
labelled with annotated tags (signed tags are annotated) of the following
format:

    v<num>(.<num>)+ [ {a|b|c|rc} <num> (.<num>)* ]

If `git describe` returns an error (likely because we're in an unpacked copy
of a release tarball, rather than a git repository), or returns a tag that
does not match the above format, the version is read from a RELEASE-VERSION
file.

To use this script, simply import it in your setup.py file and use the results
of get_version() as your package version:

    import version
    setup(
        version=version.get_version(),
        .
        .
        .
    )

This will automatically update the RELEASE-VERSION file.  The RELEASE-VERSION
file should *not* be checked into git but it *should* be included in sdist
tarballs (as should the version.py file).  To do this, run:

    echo include RELEASE-VERSION version.py >> MANIFEST.in
    echo RELEASE-VERSION >> .gitignore

With that setup, a new release can be labelled by simply invoking:

    git tag -s v1.0

The original version of this module is due to Douglas Creager, with PEP 386
modifications by Michal Nazarewicz. Here is a nice write-up of the original:

    http://dcreager.net/2010/02/10/setuptools-git-version-numbers/

"""

import re
import subprocess
import sys

__author__ = ('Douglas Creager <dcreager@dcreager.net>',
              'Michal Nazarewicz <mina86@mina86.com>',
              'Ludwig Schwardt <ludwig@ska.ac.za>')
__license__ = 'This file is placed into the public domain.'
__maintainer__ = 'Ludwig Schwardt'
__email__ = 'ludwig@ska.ac.za'

__all__ = ('get_version')

RELEASE_VERSION_FILE = 'RELEASE-VERSION'

# http://www.python.org/dev/peps/pep-0386/
_PEP386_SHORT_VERSION_RE = r'\d+(?:\.\d+)+(?:(?:[abc]|rc)\d+(?:\.\d+)*)?'
_PEP386_VERSION_RE = r'^%s(?:\.post\d+)?(?:\.dev\d+)?$' % (
    _PEP386_SHORT_VERSION_RE)
_GIT_DESCRIPTION_RE = r'^v(?P<ver>%s)-(?P<commits>\d+)-g(?P<sha>[\da-f]+)$' % (
    _PEP386_SHORT_VERSION_RE)


def read_git_version():
    try:
        proc = subprocess.Popen(('git', 'describe', '--long',
                                 '--match', 'v[0-9]*.*'),
                                stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        data, _ = proc.communicate()
        if proc.returncode:
            return
        ver = data.splitlines()[0].strip()
    except subprocess.CalledProcessError:
        return

    if not ver:
        return
    m = re.search(_GIT_DESCRIPTION_RE, ver)
    if not m:
        sys.stderr.write('version: git description (%s) is invalid, '
                         'ignoring\n' % (ver,))
        return

    commits = int(m.group('commits'))
    if not commits:
        return m.group('ver')
    else:
        return '%s.post%d.dev%d' % (
            m.group('ver'), commits, int(m.group('sha'), 16))


def read_release_version():
    try:
        fd = open(RELEASE_VERSION_FILE)
        try:
            ver = fd.readline().strip()
        finally:
            fd.close()
        if not re.search(_PEP386_VERSION_RE, ver):
            sys.stderr.write('version: release version (%s) is invalid, '
                             'will use it anyway\n' % (ver,))
        return ver
    except IOError:
        return


def write_release_version(version):
    fd = open(RELEASE_VERSION_FILE, 'w+')
    fd.write('%s\n' % (version,))
    fd.close()


def get_version():
    release_version = read_release_version()
    version = read_git_version() or release_version
    if not version:
        raise ValueError('Cannot find the version number')
    if version != release_version:
        write_release_version(version)
    return version


if __name__ == '__main__':
    print get_version()