Show type-changed files in commit diffs (#60422)

# Objective

Zed ignores files marked by Git as type-changed (T), causing commits
containing only these changes to show 0 Changed Files.

For example, commit d7cc949e61 changes
crates/eval_utils/LICENSE-GPL from a regular file to a symlink, but Zed
displays no changes.

  ## Solution

Handle TypeChanged files like modified files by loading both their old
and new contents.

  ## Testing

  - Added parser coverage for the T status.
  - Added a repository test for a regular-file-to-symlink change.
  - Ran cargo test -p git.
  - Ran ./script/clippy -p git.
  - Manually verified the example commit on macOS.

  ## Self-Review Checklist:
  - [x] I've reviewed my own diff for quality, security, and reliability
  - [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and [icon](https://github.com/zed-
  industries/zed/blob/main/crates/icons/README.md) guidelines)
  - [x] Tests cover the new/changed behavior
  - [x] Performance impact has been considered and is acceptable

  ## Showcase

Before:
<img width="200" alt="image"
src="https://github.com/user-attachments/assets/277c5938-5c2c-47b7-902d-9061a14c062a"
/>

After:
<img width="200" alt="image"
src="https://github.com/user-attachments/assets/f99d0005-0712-4843-814e-d73b11f64782"
/>

  ———

  Release Notes:

- Fixed type-changed files not appearing in Git Graph and commit views.

crates/git/src/commit.rs

@@ -109,6 +109,7 @@ pub fn parse_git_diff_name_status(content: &str) -> impl Iterator<Item = (&str,
             let path = parts.next()?;
             let status = match status_str {
                 "M" => StatusCode::Modified,
+                "T" => StatusCode::TypeChanged,
                 "A" => StatusCode::Added,
                 "D" => StatusCode::Deleted,
                 _ => continue,
@@ -127,6 +128,7 @@ mod tests {
     fn test_parse_git_diff_name_status() {
         let input = concat!(
             "M\x00Cargo.lock\x00",
+            "T\x00LICENSE-GPL\x00",
             "M\x00crates/project/Cargo.toml\x00",
             "M\x00crates/project/src/buffer_store.rs\x00",
             "D\x00crates/project/src/git.rs\x00",
@@ -142,6 +144,7 @@ mod tests {
             output,
             &[
                 ("Cargo.lock", StatusCode::Modified),
+                ("LICENSE-GPL", StatusCode::TypeChanged),
                 ("crates/project/Cargo.toml", StatusCode::Modified),
                 ("crates/project/src/buffer_store.rs", StatusCode::Modified),
                 ("crates/project/src/git.rs", StatusCode::Deleted),

crates/git/src/repository.rs

@@ -1445,7 +1445,7 @@ impl GitRepository for RealGitRepository {
                 };
 
                 match status_code {
-                    StatusCode::Modified => {
+                    StatusCode::Modified | StatusCode::TypeChanged => {
                         stdin.write_all(commit.as_bytes()).await?;
                         stdin.write_all(b":").await?;
                         stdin.write_all(path.as_bytes()).await?;
@@ -1491,7 +1491,7 @@ impl GitRepository for RealGitRepository {
                 };
 
                 match status_code {
-                    StatusCode::Modified => {
+                    StatusCode::Modified | StatusCode::TypeChanged => {
                         info_line.clear();
                         stdout.read_line(&mut info_line).await?;
                         let len = info_line.trim_end().parse().with_context(|| {
@@ -4031,6 +4031,61 @@ mod tests {
         );
     }
 
+    #[gpui::test]
+    async fn test_load_commit_with_type_changed_file(cx: &mut TestAppContext) {
+        disable_git_global_config();
+        cx.executor().allow_parking();
+
+        let repo_dir = tempfile::tempdir().expect("failed to create temporary repository");
+        git_init_repo(repo_dir.path());
+        fs::write(repo_dir.path().join("file.txt"), "regular contents\n")
+            .expect("failed to write regular file");
+        git_command(repo_dir.path(), ["add", "file.txt"]);
+        git_command(repo_dir.path(), ["commit", "-m", "initial"]);
+
+        let repository = RealGitRepository::new(
+            &repo_dir.path().join(".git"),
+            None,
+            Some("git".into()),
+            cx.executor(),
+        )
+        .expect("failed to open repository");
+        fs::write(repo_dir.path().join("file.txt"), "target")
+            .expect("failed to write symlink target");
+
+        let symlink_blob = repository
+            .git_binary()
+            .run(&["hash-object", "-w", "file.txt"])
+            .await
+            .expect("failed to write symlink blob");
+        git_command(
+            repo_dir.path(),
+            [
+                OsString::from("update-index"),
+                OsString::from("--cacheinfo"),
+                OsString::from("120000"),
+                OsString::from(symlink_blob),
+                OsString::from("file.txt"),
+            ],
+        );
+        git_command(repo_dir.path(), ["commit", "-m", "type change"]);
+
+        let commit_diff = repository
+            .load_commit("HEAD".to_string(), cx.to_async())
+            .await
+            .expect("failed to load type-changed commit");
+        assert_eq!(commit_diff.files.len(), 1);
+
+        let file = commit_diff
+            .files
+            .first()
+            .expect("type-changed file should be present");
+        assert_eq!(file.path.as_unix_str(), "file.txt");
+        assert_eq!(file.old_text.as_deref(), Some("regular contents\n"));
+        assert_eq!(file.new_text.as_deref(), Some("target"));
+        assert_eq!(file.status(), CommitFileStatus::Modified);
+    }
+
     #[gpui::test]
     async fn test_check_access(cx: &mut TestAppContext) {
         disable_git_global_config();