Add support for GitBucket

[rybak]

Overview

• Home page: https://gitbucket.github.io/
• Development is on GitHub: https://github.com/gitbucket/gitbucket

Is UI of this hosting provider a SPA?

No.

Public instances

• https://git.findnothing.cyou/ Now it's a Forgejo instance
  • Might need to find more examples, I just stumbled upon this one in GitBucket's issues
• Unfortunately, "Official demo site" is dead: https://gitbucket.herokuapp.com/

Example URLs for testing

• Regular commit:
• Commit without body in the commit message:
• Tagged commit:
• Commit at the tip of a branch:
• Commit with issue number in the subject line:
• Commit with PR number in the subject line:

TODO

• Blocker: find a public instance to test on or try running it locally
• find a commit page with a body in the commit message

Screenshot

Not sure about the location yet, because of lack of a commit with a body in the commit message => I have no idea how the UI displays it. However, the button should probably be added to the left of button "Browse code":