Populate RepositoryBranch

[MattKotsenas]

Fixes #1243.

Adds BranchName as an output of the LocateRepository task and also adds it to the SourceRoot for the main repository. The locate task maps the BranchName output task to SourceBranchName in the .targets file to follow the naming convention. The branch is the full symbolic-ref name and not the short name to avoid ambiguity in source control systems like GitHub which use the refs/pull namespace for Pull Requests.

This change doesn't add branch name to submodules, as fundamentally submodules only track commits, and the main branch will fully specify any submodule-related metadata.

The corresponding change to map this value into RepositoryBranch as part of NuGet pack is @ NuGet/NuGet.Client#5923.

Open issues in the PR:

1. Some of the CloudHostedProvidersTests.cs specifically use the inbox version of the Git tasks, and as such they can't assert the new functionality. I'm unsure if that's by design and I should not worry about that scenario, or if the tests should be changed?
2. Open to name changes anywhere; I went with the simple name, but happy to rename if there's something more appropriate.

[MattKotsenas]

/cc @tmat & @baronfel for review and questions. Thanks so much!

[baronfel]

I haven't looked in detail, but to answer the question about where the package metadata mapping should go I'd say a followup PR to NuGet would be the appropriate place - they already have the mappings for the other automatic package properties.

[MattKotsenas]

I haven't looked in detail, but to answer the question about where the package metadata mapping should go I'd say a followup PR to NuGet would be the appropriate place - they already have the mappings for the other automatic package properties.

OK, I can get started on that. Separately but relatedly, do you know the flow for updates? I'm new in this area, but to "ship" this feature end-to-end it sounds like we'd need at least:

1. Update SourceLink package
2. Update NuGet client package
3. SDK update to pull in new versions of 1 + 2

Is this a manual process, or are these picked up automatically? Any info greatly appreciated. Thanks!

[baronfel]

There's automated code flow of both SourceLink and NuGet targets into the SDK now - if you're working against main branch for all of the repos then you're targeting .NET 9 at this point, which feels fine to me.

[MattKotsenas]

Created a draft in NuGet.Client: NuGet/NuGet.Client#5923.

@tmat, would you mind taking a look, or letting me know who can review? Happy to make any changes requested. Thanks!

[tmat]

I'll take a look.

[tmat]

@MattKotsenas Looks great! Thanks for the PR. Just minor update to the comments and it's good to go.

[MattKotsenas]

Thanks @tmat! I believe I fixed all your comments. Would you mind taking another look?