feat(jj): add module for Jujutsu current change ID

[poliorcetics]

Description

Adds support for getting and displaying the current Jujutsu change ID (when in a Jujutsu repo)

Motivation and Context

Jujutsu is a new VCS that is change-based.

I want to do several PRs to add various parts of its informations to starship, starting with the simplest one, the current change ID.

Screenshots (if appropriate):

Explained prompt, with the JJ change ID module:

Result of explained prompt above:

How Has This Been Tested?

• I have tested using MacOS
• I have tested using Linux
• I have tested using Windows

Checklist:

• I have updated the documentation accordingly.
• I have updated the tests accordingly.

[poliorcetics]

I see #5772 exists, it uses the approach of computing everything at once and only displaying the wanted elements, I'm not sure which starship prefers

[necauqua]

I'd strongly prefer the jj calls would have --ignore-working-copy to avoid snapshots being made literally on every prompt. Somebody might want it I guess, but at least make it configurable then.

Not snapshotting works fine for change ids and branches, for diffs you'd either give up and do snapshots or wait for --no--commit-transaction option to be a thing

edit: well that other PR does this and more, oh well :)

[poliorcetics]

@necauqua you're right, and --ignore-working-copy is much faster too.

I also added the --repository, I though it would interfere with testing but since I mocked jj root too, it doesn't 🎉

The step has gone from 48ms before to 35ms with those

[ckoehler]

Would love to also be able to indicate whether the change is empty or missing a description. Thanks! Happy to help move this along...