Increment Google App Engine app version string. If each deploy is a unique version, App Engine deploys are zero risk thanks to version routing.

increment_version.py

#!/usr/bin/env python

import argparse
import yaml


def increment_version(version, inc_major=None, inc_minor=None, sep='-'):
    version_string = str(version)
    if '-' in version_string:
        major, minor = version_string.split('-')
    else:
        major = version_string
        minor = 0
    try:
        if inc_major:
            major = int(major) + 1
        if inc_minor:
            minor = int(minor) + 1
    except ValueError:
        raise SystemExit('Bad version string format! Format is: "1" or "1-0"')
    return sep.join([str(major), str(minor)])

description = '''\
increment Appengine app version string in app.yaml.
version string format must be:
   "1" or "2-1"'''


parser = argparse.ArgumentParser(
    formatter_class=argparse.RawDescriptionHelpFormatter,
    description=description)

parser.add_argument('path', help='Appengine yaml file')
parser.add_argument('--major', action='store_true',
                    help='Increment major version')
parser.add_argument('--minor', action='store_true', default=True,
                        help='Increment minor version')
args = parser.parse_args()

with open(args.path) as f:
    data = yaml.load(f)
version = increment_version(data['version'], args.major, args.minor)
data['version'] = version
print yaml.dump(data)