Fix not able to navigate to files in git commit multibuffer (#42558)

Closes #40851

Release Notes:

- Fixed: Commit diff multibuffers now open real project files whenever
possible, restoring navigation and annotations inside those excerpts.

---------

Co-authored-by: Anthony Eid <anthony@zed.dev>

crates/editor/src/editor.rs

@@ -21936,10 +21936,17 @@ impl Editor {
                 };
 
                 for (buffer, (ranges, scroll_offset)) in new_selections_by_buffer {
-                    let editor = buffer
-                        .read(cx)
-                        .file()
-                        .is_none()
+                    let buffer_read = buffer.read(cx);
+                    let (has_file, is_project_file) = if let Some(file) = buffer_read.file() {
+                        (true, project::File::from_dyn(Some(file)).is_some())
+                    } else {
+                        (false, false)
+                    };
+
+                    // If project file is none workspace.open_project_item will fail to open the excerpt
+                    // in a pre existing workspace item if one exists, because Buffer entity_id will be None
+                    // so we check if there's a tab match in that case first
+                    let editor = (!has_file || !is_project_file)
                         .then(|| {
                             // Handle file-less buffers separately: those are not really the project items, so won't have a project path or entity id,
                             // so `workspace.open_project_item` will never find them, always opening a new editor.
@@ -21973,6 +21980,9 @@ impl Editor {
                         });
 
                     editor.update(cx, |editor, cx| {
+                        if has_file && !is_project_file {
+                            editor.set_read_only(true);
+                        }
                         let autoscroll = match scroll_offset {
                             Some(scroll_offset) => Autoscroll::top_relative(scroll_offset as usize),
                             None => Autoscroll::newest(),
@@ -21996,10 +22006,11 @@ impl Editor {
         });
     }
 
-    // For now, don't allow opening excerpts in buffers that aren't backed by
-    // regular project files.
+    // Allow opening excerpts for buffers that either belong to the current project
+    // or represent synthetic/non-local files (e.g., git blobs). File-less buffers
+    // are also supported so tests and other in-memory views keep working.
     fn can_open_excerpts_in_file(file: Option<&Arc<dyn language::File>>) -> bool {
-        file.is_none_or(|file| project::File::from_dyn(Some(file)).is_some())
+        file.is_none_or(|file| project::File::from_dyn(Some(file)).is_some() || !file.is_local())
     }
 
     fn marked_text_ranges(&self, cx: &App) -> Option<Vec<Range<MultiBufferOffsetUtf16>>> {

crates/editor/src/items.rs

@@ -1891,15 +1891,20 @@ fn path_for_buffer<'a>(
     cx: &'a App,
 ) -> Option<Cow<'a, str>> {
     let file = buffer.read(cx).as_singleton()?.read(cx).file()?;
-    path_for_file(file.as_ref(), height, include_filename, cx)
+    path_for_file(file, height, include_filename, cx)
 }
 
 fn path_for_file<'a>(
-    file: &'a dyn language::File,
+    file: &'a Arc<dyn language::File>,
     mut height: usize,
     include_filename: bool,
     cx: &'a App,
 ) -> Option<Cow<'a, str>> {
+    if project::File::from_dyn(Some(file)).is_none() {
+        return None;
+    }
+
+    let file = file.as_ref();
     // Ensure we always render at least the filename.
     height += 1;
 
@@ -1946,11 +1951,11 @@ mod tests {
 
     #[gpui::test]
     fn test_path_for_file(cx: &mut App) {
-        let file = TestFile {
+        let file: Arc<dyn language::File> = Arc::new(TestFile {
             path: RelPath::empty().into(),
             root_name: String::new(),
             local_root: None,
-        };
+        });
         assert_eq!(path_for_file(&file, 0, false, cx), None);
     }
 

crates/git_ui/src/commit_view.rs

@@ -68,6 +68,7 @@ struct GitBlob {
     path: RepoPath,
     worktree_id: WorktreeId,
     is_deleted: bool,
+    display_name: Arc<str>,
 }
 
 const FILE_NAMESPACE_SORT_PREFIX: u64 = 1;
@@ -157,6 +158,7 @@ impl CommitView {
             });
             editor
         });
+        let commit_sha = Arc::<str>::from(commit.sha.as_ref());
 
         let first_worktree_id = project
             .read(cx)
@@ -180,10 +182,20 @@ impl CommitView {
                             .or(first_worktree_id)
                     })?
                     .context("project has no worktrees")?;
+                let short_sha = commit_sha.get(0..7).unwrap_or(&commit_sha);
+                let file_name = file
+                    .path
+                    .file_name()
+                    .map(|name| name.to_string())
+                    .unwrap_or_else(|| file.path.display(PathStyle::Posix).to_string());
+                let display_name: Arc<str> =
+                    Arc::from(format!("{short_sha} - {file_name}").into_boxed_str());
+
                 let file = Arc::new(GitBlob {
                     path: file.path.clone(),
                     is_deleted,
                     worktree_id,
+                    display_name,
                 }) as Arc<dyn language::File>;
 
                 let buffer = build_buffer(new_text, file, &language_registry, cx).await?;
@@ -647,7 +659,7 @@ impl language::File for GitBlob {
     }
 
     fn file_name<'a>(&'a self, _: &'a App) -> &'a str {
-        self.path.file_name().unwrap()
+        self.display_name.as_ref()
     }
 
     fn worktree_id(&self, _: &App) -> WorktreeId {