Unified diff in the switch picker

Review finding

Change surface

Risk is concentrated in the Git repository layer and picker runtime. Tests, documentation, and benchmarks account for most of the remaining files.

Files

46

Hunks

191

Commits

6

Changed lines

2,268

Patch lines

4,126

Patch bytes

214 KB

max-sixty/worktrunk #3865
  src/
    commands/picker/  17 files  +823 −466
    git/repository/    4 files  +312 −30
    other              6 files  +42  −61
  tests/               8 files  +308 −92
  docs + shipped skills
                       9 files  +69  −42
  benches/             2 files  +13  −10

What changes at runtime

The behavior view keeps the picker path fixed and changes the default preview in place. The call view is a scoped static analysis of the orchestration file, so every source coordinate leads back to the exact patch.

flowchart TB
  accTitle: Unified diff preparation
  accDescr: A selected row chooses a preview mode. Unified diff uses PreparedDiff for committed changes and TempIndex for staged, unstaged and untracked work; working and committed tabs remain available.
  Row[Selected row] --> Mode[Preview mode]
  Mode -. old default .-> Working["− working-tree diff"]
  Mode --> Unified["+ unified diff"]
  Mode --> Tabs[Working / committed tabs]
  Unified --> Prepared[PreparedDiff]
  Prepared --> History[Committed changes]
  Prepared --> Temp[TempIndex]
  Temp --> Staged[Staged]
  Temp --> Unstaged[Unstaged]
  Temp --> Untracked[Untracked]
  classDef removed fill:var(--del-tint),stroke:var(--danger),color:var(--danger)
  classDef added fill:var(--ok-tint),stroke:var(--ok),color:var(--ok-ink)
  class Working removed
  class Unified,Prepared,Temp added

The orchestration hunk the picker uses

This exact hunk from src/summary.rs replaces direct Git argument assembly with the repository’s PreparedDiff API.

diff --git a/src/summary.rs b/src/summary.rs
index b856171b57..cfa4f0448e 100644
--- a/src/summary.rs
+++ b/src/summary.rs
@@ -258,16 +256,14 @@ pub(crate) fn compute_combined_diff(
 
     // Working tree diff: uncommitted changes
     if let Some(wt_path) = worktree_path {
-        let path = wt_path.display().to_string();
-        if let Ok(wt_stat) = repo.run_command(&["-C", &path, "diff", "HEAD", "--stat"])
+        let prepared = repo.worktree_at(wt_path).prepare_diff(["HEAD"]);
+        if let Ok(wt_stat) = prepared.capture(["--stat"])
             && !wt_stat.trim().is_empty()
         {
             stat.push_str(&wt_stat);
         }
-        let mut wt_diff_args = vec!["-C", &path];
-        wt_diff_args.extend(DIFF_PREFIX_OVERRIDES);
-        wt_diff_args.extend(["diff", "HEAD"]);
-        if let Ok(wt_diff) = repo.run_command(&wt_diff_args)
+        if let Ok(wt_diff) =
+            prepared.capture_with_git_options(DIFF_PREFIX_OVERRIDES, std::iter::empty::<&str>())
             && !wt_diff.trim().is_empty()
         {
             diff.push_str(&wt_diff);

Review invariants

Exact excerpts from revision 9ca8f78b show the byte-equality and scheduling tests, followed by the temporary-index implementation.

Real index byte equality

src/commands/picker/items.rs · unified_diff_is_net_change_and_subsidiary_diffs_include_untracked

        let real_index = repo.current_worktree().git_dir().unwrap().join("index");
        let index_before = std::fs::read(&real_index).unwrap();
        let unified = PickerRow::compute_unified_diff_preview(&repo, &item, 80);
        let working = PickerRow::compute_working_tree_preview(&repo, &item, 80);
        let committed = PickerRow::compute_branch_diff_preview(&repo, &item, 80);
        let index_after = std::fs::read(&real_index).unwrap();
        assert_eq!(
            index_after, index_before,
            "preview computation must leave the real index byte-identical"
        );

Off-screen worktree scheduling

src/commands/picker/preview_orchestrator.rs · initial_precompute_skips_offscreen_worktrees_but_warms_branches

        orch.spawn_initial_precompute(
            &orch.generation(),
            &[first, Arc::clone(&offscreen), Arc::clone(&branch)],
            (80, 24),
            None,
        );
        orch.wait_for_idle();

        assert!(
            !orch
                .cache
                .contains_key(&("offscreen".to_string(), PreviewMode::UnifiedDiff)),
            "off-screen worktree should wait for selected-row demand"
        );
        assert!(
            orch.cache
                .contains_key(&("branch-only".to_string(), PreviewMode::UnifiedDiff)),
            "branch-only default should be prewarmed from the committed diff"
        );

Temporary-index implementation evidence

src/git/repository/working_tree.rs · WorkingTree::temp_index

        let mut temp_file = tempfile::Builder::new()
            .prefix(TEMP_INDEX_PREFIX)
            .tempfile()
            .context("Failed to create temporary index")?;
        let mut real_index_file = match std::fs::File::open(&real_index) {
            Ok(file) => Some(file),
            Err(error) if error.kind() == std::io::ErrorKind::NotFound => None,
            Err(error) => return Err(error).context("Failed to open index file"),
        };
        if let Some(real_index_file) = &mut real_index_file {
            std::io::copy(real_index_file, temp_file.as_file_mut())
                .context("Failed to copy index file")?;
        }
        let temp = temp_file.into_temp_path();

Evidence and remaining gaps

Exact patch · 46 files

GitHub’s captured patch for revision 9ca8f78b. All 46 files start closed and remain independently commentable.

Review in place. Alt-click a file header or source line to comment on that whole target, or drag across an exact expression to quote it. Comments retain their file coordinate—and, for line comments, side, line, and quote—even when the file disclosure is closed.

Captured pull request

Review history

1. 03:32 UTC observation PR opened The first revision introduced the unified picker tab, shared diff preparation, and broad integration coverage.
2. 03:43 UTC warning First review withheld approval It found divergent sparse handling, a predictable shared temp directory, startup-cost uncertainty, and documentation drift.
3. 04:13 UTC intervention Temp indexes became random, exclusive files Sparse registration and worktree-local temp-directory exclusion gained focused tests.
4. 04:32 UTC intervention The index copy kept ownership of its pathname Writing through the still-open file closed the symlink race, and off-screen worktrees moved out of eager prewarm.
5. 04:57 UTC observation Agent review recommends approval with follow-ups The shared TempIndex path and orchestration prose converged; selected-row latency and dry-run temp artifacts remained visible notes.