use struct-based SourceMetadataFunc signature across git sources

[amanfcp]

Description:

• Refactor SourceMetadataFunc from a 7-parameter function to a struct-based SourceMetadataInfo approach
• Add LegacySourceMetadataFunc wrapper for backward compatibility with EE consumers
• Update all OSS git-based source implementations (GitHub, GitLab, HuggingFace, GitHub Experimental, snifftest)

Benefits

• Future extensibility: Adding new metadata fields (e.g. Branch) no longer requires changing the function signature across all consumers
• Backward compatibility: LegacySourceMetadataFunc allows gradual EE migration

Testing

• Existing tests pass unchanged — refactoring is type-level only with no behavioral modifications

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?

---

Note

Low Risk
Low risk type-level refactor, but it touches core git scanning paths; any missed field mapping could degrade metadata (links/line numbers) across sources.

Overview
Refactors git metadata callback plumbing by replacing the 7-parameter SourceMetadataFunc with a struct-based SourceMetadataInfo, making the callback signature extensible without widespread breaking changes.

Updates git chunk/commit/staged scanning code to construct and pass SourceMetadataInfo (including RepositoryLocalPath/Line where relevant), and migrates OSS consumers (github, gitlab, huggingface, github_experimental, and hack/snifftest) to the new callback shape while preserving existing metadata fields/links.

^{Written by Cursor Bugbot for commit b160a79. This will update automatically on new commits. Configure here.}

[rosecodym]

This is super cool, thanks! I appreciate the addition of the deprecated wrapper function to ease legacy conversion, but I wanted to note that using it might not end up being any less work than modifying the underlying functions directly once we bring this in.