Add walker for jujutsu repositories

[delafthi]

Is your feature request related to a problem? Please describe.

I'm working with Jujutsu repositories, and currently, numtide/treefmt does not provide a dedicated walker for Jujutsu repositories (without co-location). As a result, treefmt does not correctly respect Jujutsu’s ignore files (local and global Git ignore files).

Describe the solution you'd like

I would like to see a dedicated walker for Jujutsu repositories in numtide/treefmt that fully respects Jujutsu's ignore mechanisms.

Describe alternatives you've considered

As an alternative, using a co-located Jujutsu repository alongside Git allows treefmt to use the existing Git walker. However, this setup introduces a slight overhead, as described here.

Additional context

Jujutsu’s workflow differs significantly from Git’s, which may cause differences in walker behavior. I have started experimenting with an implementation #601, although I lack Go experience and primarily copied, and adapted the existing Git walker by adjusting commands. I would welcome guidance or collaboration to develop a more idiomatic and robust implementation.

[brianmcgee]

Thanks for taking the time, happy to review what you've done. Be warned, it might take me a while to get around to having a look, my workload is quite high at the moment.

[delafthi]

Thanks for taking the time, happy to review what you've done. Be warned, it might take me a while to get around to having a look, my workload is quite high at the moment.

At the moment, I am still debugging some issues; the tests are not passing yet. I will keep the PR as a draft until it's ready for review.

What I’m most interested in getting your feedback on is the following question:

• Do you think this is generally the right approach, I mean copy/pasting the github walker and adapting it?

[jfly]

@delafthi I just gave you a preliminary review. The approach you're taking looks good to me.