python-semantic-release should have an option to pull version_variable from git tag

python-semantic-release should have an option to pull version_variable from git tag

python-semantic-release requires version_variable to be in a file and bumps and auto-commits it.

For parity with semantic-release per https://semantic-release.gitbook.io/semantic-release/support/faq#why-is-the-package-jsons-version-not-updated-in-my-repository semantic release updates package.json then prepares and publishes the package and doesn’t auto-commit the version change.

This is desirable for CI so that auto-commits don’t require troublesome exceptions to prevent an infinite loop of version bumps.

If we don’t push the commit to the version_variable subsequent runs report the following error

Creating new version..
Current version: 0.0.0
Cmd('git') failed due to: exit code(128)
  cmdline: git tag -m v0.0.1 -a v0.0.1
  stderr: 'fatal: tag 'v0.0.1' already exists'

[fattybenji]

Renamed commit_changes to commit_version_number

See https://github.com/relekang/python-semantic-release/pull/143#pullrequestreview-283235383

[fattybenji]

Ok, I’m going to do the following :

• If version_source is commit, will get version from version_variable file and edit the file with the new version. If variable commit_changes is defined and False, won’t commit. If it is undefined or True, will commit and push changes.
• If version_source is tag, will get version from VCS and will edit the file defined in version_variable. If the file doesn’t exist, will fail silently (backwards compatibility). If variable commit_changes is defined and True, will commit and push changes. If it is undefined or False, won’t push.

I intend to do that by setting the actual value of commit_changes as :

commit_changes = config.get('semantic_release', 'commit_changes', fallback=(version_source == 'commit'))

This way, we will have a full backward compatibility with the current behavior, while giving people the choice to do differently. This can be discussed when I submit the PR.