Resolve file paths relative to repo root

[hassaanm]

Summary

This pull request allows lumen to run correctly from a sub directory. Currently, it can't find the files correctly and treats them as being deleted.

Changes

• Add get_repository_root() method to VcsBackend trait
• Implement for GitBackend (using repo.workdir()) and JjBackend (using workspace_path)
• Update get_new_content() to resolve paths from repo root

Test plan

• Added test_get_repository_root_from_subdirectory for GitBackend
• Added test_load_file_diffs_from_subdirectory integration test
• Manually verified on an existing git repo but couldn't verify on a jj repo (see Notes section below)

Repro steps

1. Go to a sub directory
2. Make a change to a file
3. Run lumen diff

Notes

Discovered a pre-existing issue: JjBackend cannot be loaded from subdirectories because Workspace::load() requires the exact workspace root path (unlike git2's Repository::discover() which walks up the directory tree). This is unrelated to this fix - the same error occurs on the current release.

Summary by CodeRabbit

• Bug Fixes

  • Corrected file diff/new-content resolution when running the tool from a subdirectory — diffs and updated content are now resolved against the repository root.

• Tests

  • Added tests to verify diffs and file content are correctly loaded when operating from within repository subdirectories.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds VcsBackend::get_repository_root and implements it for Git and Jj backends; diff logic now resolves working-tree file reads against the repository root with a fallback to the original filename. Tests added to verify root resolution from subdirectories.

Changes

Cohort / File(s)	Summary
Vcs trait src/vcs/backend.rs	Added fn get_repository_root(&self) -> Result<std::path::PathBuf, VcsError> to VcsBackend.
Git backend src/vcs/git.rs	Added get_repository_root() for GitBackend (returns repo root or error for bare repo). Added unit tests verifying resolution from a subdirectory.
Jj backend src/vcs/jj.rs	Implemented get_repository_root() for JjBackend (returns workspace_root).
Diff logic & tests src/command/diff/git.rs	WorkingTree::get_new_content now resolves filenames against backend.get_repository_root() and falls back to the original path. Added test test_load_file_diffs_from_subdirectory.

Sequence Diagram(s)

sequenceDiagram
  participant CLI as CLI/Command
  participant Diff as diff::git::WorkingTree
  participant VCS as VcsBackend
  participant FS as Filesystem

  CLI->>Diff: request file diff
  Diff->>VCS: get_repository_root()
  VCS-->>Diff: repository root path
  Diff->>FS: read file at (repo_root + filename)
  alt read succeeds
    FS-->>Diff: new_content
  else fallback
    Diff->>FS: read file at original filename
    FS-->>Diff: new_content or error
  end
  Diff-->>CLI: return diff result (includes new_content)

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• feat(vcs): implement GitBackend for git CLI integration #89 — Extends VcsBackend and backend implementations; touches the same trait/backends updated here.
• feat(vcs): migrate GitBackend from CLI to git2 (libgit2) #98 — Modifies Git backend repository discovery/initialization logic related to repository-root handling.
• feat(vcs): add VcsBackend trait and VCS detection module #88 — Introduced the VcsBackend abstraction that this change extends.

Suggested reviewers

• jnsahaj

Poem

🐰 I hopped from subdir, nose to root,

I sniffed the path, then gave a toot.
Files now found where roots abide,
Diffs no longer lose their stride.
🥕

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 45.45% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: resolving file paths relative to the repository root instead of the current working directory.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/vcs/jj.rs`:
- Around line 973-975: get_repository_root currently returns the stored
self.workspace_path which may be a subdirectory; change get_repository_root to
return the actual workspace root by calling
self.workspace.workspace_root().to_path_buf() instead of using
self.workspace_path so the function returns the correct root loaded by the
Workspace (update the body of fn get_repository_root to return
Ok(self.workspace.workspace_root().to_path_buf())).

[Straffern]

This might be duplicate of: #110
My PR was implemented by llm, so if you know Rust, your solution might be better.

[hassaanm]

Oh nice. I'm not too familiar with rust either. My pull request was ai assisted. I built and tested it locally for verification to help build confidence. I'll be happy if either pull request gets merged haha.