Add commitPrefix for defining a prefix for any project

[duckbrain]

• PR Description

Adds a new option git.comitPrefix to act similarly to git.commitPrefixes, except, if defined, it applies to any repo that doesn't have an entry in git.commitPrefixes.

• Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• Docs (specifically docs/Config.md) have been updated if necessary
• You've read through your own file changes for silly mistakes etc

[duckbrain]

See:

#2759
#1941

[stefanhaller]

Makes sense to me. (I haven't looked at the code yet, though.)

As a followup I propose to support per-repo config files (see #3293) and get rid of the commitPrefixes option.

[duckbrain]

As a followup I propose to support per-repo config files (see #3293) and get rid of the commitPrefixes option.

Was this an ask for this PR or future plans? I had been understanding the latter. I agree that's a sensible way to move forward, but it seems out of scope to do that all at once.

[stefanhaller]

No, not for this one. Is "followup" not a commonly used term in software development? At work we use it for things that we will do in a separate PR later.

One of these days I'll actually get around to reviewing this PR, sorry that it fell through the cracks. Feel free to ping earlier when a PR doesn't get reviewed!

[stefanhaller]

Looks good, great work. I took the liberty to squash all commits into one, I think it makes sense in this case. Also rebased on master in order to be able to merge.

Sorry again for the long delay in reviewing this.