gitver2deb

#!/usr/bin/env python3
# Copyright 2018 dunnhumby Germany GmbH.
# Distributed under the Boost Software License, Version 1.0.
# (See accompanying file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)

# This converts version from `git describe`-style SemVer versions to Debian
# compatible version.
#
# The input version is take from STDIN and is expected to be in the form:
# [v]<upstream_version>[-<C>-g<H>][-dirty]
#
# Where:
#
# <upstream_version>
#   Is the current version of the project, expected to be the last tag, which
#   should be SemVer compatible, or a branch name.
#   It will be parsed as a SemVer version:
#     <X>.<Y>.<Z>[-<pre_release>][+<metadata>]
#   If the parsing is not successful, <X>, <Y> and <Z> are interpreted as 0 and
#   the <pre_release> is set to `git.<upstream_version>` (so is interpreted as
#   a 0.0.0 pre-release). In this case any non-alphanumeric character that is
#   not compatible with the SemVer character set allowed for pre-releases is
#   replaced by `.`.
#
#   Also the `-` chars in <pre_release> and <metadata> is translated to `.` (as
#   `-` has a special meaning for Debian versions).
#
# <C>
#   Is how many commits ahead of the last tag the project is.
#
# <H>
#  Is the hash of the current version's commit.
#
# Parts between [] are optional.
#
# The translated version is then constructed as:
# <X>.<Y>.<Z>[~<pre_release>][+<C>][+dirty.<date>][~<H>][~<metadata>]
#
# Where:
#
# <date> is the current date in YYYYmmddHHMMSS format.
#
# Some references:
#
# - Debian version specification:
#   https://www.debian.org/doc/debian-policy/#version
#
# - Debian versions can be compared for debugging purposes using:
#   dpkg --compare-versions <A> [eq|ge|le|gt|lt] <B>
#
# - SemVer:
#   https://semver.org/

import re
import sys
import datetime
import subprocess

DEBUG = False

git_describe_re = re.compile(
        r'^(?P<last_tag>.+?)'
        r'(?:'
            r'-(?P<commits_ahead>\d+)'
            r'-g(?P<commit_hash>[0-9a-fA-F]{4,})'
        r')?'
        r'(?:-(?P<dirty>dirty))?$'
)

semver_chars = r'0-9A-Za-z\.-'

semver_re = re.compile(
        r'^v?(?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)'
        r'(?:-(?P<pre_release>[{0}]+))?'
        r'(?:\+(?P<metadata>[{0}]+))?$'.format(semver_chars)
)

version = sys.stdin.read().strip()

major = '0'
minor = '0'
patch = '0'
pre_release = ''
metadata = ''
commits_ahead = ''
commit_hash = ''
dirty = ''

git_match = git_describe_re.match(version)
if git_match:
    version = git_match.group('last_tag')
    commits_ahead = git_match.group('commits_ahead')
    commit_hash = git_match.group('commit_hash')
    dirty = git_match.group('dirty')

semver_match = semver_re.match(version)
if semver_match:
    major = semver_match.group('major')
    minor = semver_match.group('minor')
    patch = semver_match.group('patch')
    pre_release = semver_match.group('pre_release')
    metadata = semver_match.group('metadata')
else:
    pre_release = 'git.' + re.sub('[^' + semver_chars + ']', '.', version)

if DEBUG:
    sys.stderr.write("major={!r} minor={!r} patch={!r} "
            "pre_release={!r} metadata={!r} "
            "commits_ahead={!r} commit_hash={!r} dirty={!r}\n".format(
                major, minor, patch, pre_release, metadata,
                commits_ahead, commit_hash, dirty))

version = '{}.{}.{}'.format(major, minor, patch)
if pre_release:
    version += '~' + pre_release.replace('-', '.')
if commits_ahead:
    version += '+' + commits_ahead
if dirty:
    version += '+dirty.{:%Y%m%d%H%M%S}'.format(datetime.datetime.now())
if commit_hash:
    version += '~' + commit_hash
if metadata:
    version += '~' + metadata.replace('-', '.')

print(version)