[gen_changelog] : add an option -p for a patch release

What does this MR do?

This adds a new switch to be used when releasing a patch version. Indeed, releasing a patch version is different than releasing a major or minor version. All commits in the changelog lie in the direct ancestors instead of the commits in the dev branch.

How to test it?

Generate a changelog for a major or minor release:

gen_changelog.py 17.1.0 17.2.0

Generate a changelog for a patch release:

gen_changelog.py -p 17.1.0 17.1.1

Associated Issues/Merge Requests

• Merge requests
  • sight-gitlab!4