bump_release

#!/usr/bin/env python3

"""
A program to increment the major.minor.build numbers for a GitHub project.

Usage: bump_release [-M|--major] [-m|--minor] [-b|--build]

where -M | --major   bumps the major number, & zeros minor+build
      -m | --minor   bumps the minor number, & zeros build
      -b | --build   bumps the build number (the default)

Release numbers are found in:

* the latest git tag
* setup.py

Check that the numbers from all sources are consistent, bump the release 
number as required, rewrite setup.py to use the new number and prints
the new release number to stdout.
"""

import sys
import os.path
import getopt
import subprocess


# name of the config file
TagConfigFile = 'setup.py'

# variables indicating which number to bump
(BumpMajor, BumpMinor, BumpBuild) = range(3)


def abort(msg):
    """Print a message and abort."""

    delim = '*' * 60
    print(delim)
    print(msg)
    print(delim)
    sys.exit(1)

def setup_tag():
    """Get the configured tag number from the setup file."""

    # assume data doesn't exist in file
    version_line = None
    download_line = None

    # read the expected tag number lines
    with open(TagConfigFile) as fd:
        for line in fd:
            line = line.strip()
            if line.startswith('version='):
                version_line = line
            if line.startswith('download_url='):
                download_line = line

    # make sure we got both
    if version_line is None or download_line is None:
        msg = (f"Can't find tag numbers in {TagConfigFile}:\n"
               f"version_line={version_line}\n"
               f"download_line={download_line}")
        abort(msg)

    # extract the release numbers from string, check they are the same
    #     version_line=version='4.0.5',
    #     download_url='https://github.com/rzzzwilson/pySlip/releases/tag/4.0.5',
    version_tag = version_line.split("'")[1]
    download_tag = os.path.basename(download_line.split("'")[1])
    if version_tag != download_tag:
        msg = f"Different release numbers in {TagConfigFile}: '{version_tag}' and '{download_tag}'"
        abort(msg)

    return version_tag

def write_tag(new_tag):
    """Update the config file with the new release number."""

    # read all lines from the config file
    with open(TagConfigFile) as fd:
        config_data = fd.readlines()

    # open the file for output, emit modified lines
    #     version='4.0.5',
    #     download_url='https://github.com/rzzzwilson/pySlip/releases/tag/4.0.5',
    with open(TagConfigFile, 'w') as fd:
        for line in config_data:
            line = line.rstrip(',')
            line_strip = line.strip()
            if line_strip.startswith('version='):
                (prefix, _) = line.split('=')
                line = f"{prefix}='{new_tag}',\n"
            if line_strip.startswith('download_url='):
                (prefix, path) = line.split('=')
                dirname = os.path.dirname(path)
                line = f"{prefix}={dirname}/{new_tag}',\n"
            fd.write(line)

def latest_tag():
    """Get the latest tag release number."""

    p = subprocess.check_output(['git', 'describe'], text=True)
    try:
        (tag, _) = p.split('-', maxsplit=1)
    except ValueError:
        return None
    return tag

def main(bump_what):
    """Bump the release number according to 'bump_what'."""

    # get the latest git tag number
    git_tag = latest_tag()
    if git_tag is None:
        abort('No release tag number set!?')

    # get tag numbers from setup.py
    config_tag = setup_tag()

    # check tag numbers are the same
    if git_tag != config_tag:
        abort(f'Tags are inconsistent: git_tag={git_tag}, config_tag={config_tag}')

    # bump the appropriate part of the old release number
    (major, minor, build) = git_tag.split('.')
    if bump_what == BumpMajor:
        new_tag = f'{int(major)+1}.0.0'
    elif bump_what == BumpMinor:
        new_tag = f'{major}.{int(minor)+1}.0'
    else:
        new_tag = f'{major}.{minor}.{int(build)+1}'

    # rewrite the config file to use new release number
    write_tag(new_tag)

    # return the new release number
    return new_tag

def usage(msg=None):
    """Print program help with optional message."""

    if msg:
        delim = '=' * 60
        print(delim)
        print(msg)
        print(delim)
    print(__doc__)

# parse the CLI params
argv = sys.argv[1:]

try:
    (opts, args) = getopt.getopt(argv, 'bmMh',
                                 ['build', 'minor', 'major', 'help'])
except getopt.error:
    usage()
    sys.exit(1)

bump_part = BumpBuild

for (opt, param) in opts:
    if opt in ['-b', '--build']:
        bump_part = BumpBuild
    elif opt in ['-m', '--minor']:
        bump_part = BumpMinor
    elif opt in ['-M', '--major']:
        bump_part = BumpMajor
    elif opt in ['-h', '--help']:
        usage()
        sys.exit(0)

# print the new release number to stdout
print(main(bump_part))