Add a prototype with a multi buffer having all project git changes (#21543)

Part of https://github.com/zed-industries/zed/issues/20925

This prototype is behind a feature flag and being merged to avoid
conflicts with further git-related resturctures.
To be a proper, public feature, this needs at least:
* showing deleted files
* better performance 
* randomized tests
* `TODO`s in the `project_diff.rs` file fixed

The good thing is, >90% of the changes are in the `project_diff.rs` file
only, have a basic test and already work on simple cases.

Release Notes:

- N/A

---------

Co-authored-by: Thorsten Ball <thorsten@zed.dev>
Co-authored-by: Cole Miller <cole@zed.dev>

Cargo.lock

@@ -3790,6 +3790,7 @@ dependencies = [
  "db",
  "emojis",
  "env_logger 0.11.5",
+ "feature_flags",
  "file_icons",
  "fs",
  "futures 0.3.31",
@@ -3823,6 +3824,7 @@ dependencies = [
  "snippet",
  "sum_tree",
  "task",
+ "tempfile",
  "text",
  "theme",
  "time",

crates/editor/Cargo.toml

@@ -39,6 +39,7 @@ collections.workspace = true
 convert_case.workspace = true
 db.workspace = true
 emojis.workspace = true
+feature_flags.workspace = true
 file_icons.workspace = true
 futures.workspace = true
 fuzzy.workspace = true
@@ -97,6 +98,7 @@ project = { workspace = true, features = ["test-support"] }
 release_channel.workspace = true
 rand.workspace = true
 settings = { workspace = true, features = ["test-support"] }
+tempfile.workspace = true
 text = { workspace = true, features = ["test-support"] }
 theme = { workspace = true, features = ["test-support"] }
 tree-sitter-html.workspace = true

crates/editor/src/editor.rs

@@ -327,6 +327,7 @@ pub fn init(cx: &mut AppContext) {
             .detach();
         }
     });
+    git::project_diff::init(cx);
 }
 
 pub struct SearchWithinRange;

crates/editor/src/git.rs

@@ -1 +1,2 @@
 pub mod blame;
+pub mod project_diff;

crates/editor/src/git/blame.rs

@@ -154,7 +154,7 @@ impl GitBlame {
                         this.generate(cx);
                     }
                 }
-                project::Event::WorktreeUpdatedGitRepositories => {
+                project::Event::WorktreeUpdatedGitRepositories(_) => {
                     log::debug!("Status of git repositories updated. Regenerating blame data...",);
                     this.generate(cx);
                 }

crates/file_finder/src/file_finder.rs

@@ -648,7 +648,7 @@ impl FileFinderDelegate {
         cx.subscribe(project, |file_finder, _, event, cx| {
             match event {
                 project::Event::WorktreeUpdatedEntries(_, _)
-                | project::Event::WorktreeAdded
+                | project::Event::WorktreeAdded(_)
                 | project::Event::WorktreeRemoved(_) => file_finder
                     .picker
                     .update(cx, |picker, cx| picker.refresh(cx)),

crates/git/src/diff.rs

@@ -80,7 +80,6 @@ impl BufferDiff {
         self.tree.is_empty()
     }
 
-    #[cfg(any(test, feature = "test-support"))]
     pub fn hunks_in_row_range<'a>(
         &'a self,
         range: Range<u32>,

crates/language/src/buffer.rs

@@ -3998,7 +3998,6 @@ impl BufferSnapshot {
     }
 
     /// Returns all the Git diff hunks intersecting the given row range.
-    #[cfg(any(test, feature = "test-support"))]
     pub fn git_diff_hunks_in_row_range(
         &self,
         range: Range<BufferRow>,

crates/project/src/project.rs

@@ -240,11 +240,11 @@ pub enum Event {
     LanguageNotFound(Model<Buffer>),
     ActiveEntryChanged(Option<ProjectEntryId>),
     ActivateProjectPanel,
-    WorktreeAdded,
+    WorktreeAdded(WorktreeId),
     WorktreeOrderChanged,
     WorktreeRemoved(WorktreeId),
     WorktreeUpdatedEntries(WorktreeId, UpdatedEntriesSet),
-    WorktreeUpdatedGitRepositories,
+    WorktreeUpdatedGitRepositories(WorktreeId),
     DiskBasedDiagnosticsStarted {
         language_server_id: LanguageServerId,
     },
@@ -259,7 +259,7 @@ pub enum Event {
     DisconnectedFromHost,
     DisconnectedFromSshRemote,
     Closed,
-    DeletedEntry(ProjectEntryId),
+    DeletedEntry(WorktreeId, ProjectEntryId),
     CollaboratorUpdated {
         old_peer_id: proto::PeerId,
         new_peer_id: proto::PeerId,
@@ -1504,6 +1504,7 @@ impl Project {
         cx: &mut ModelContext<Self>,
     ) -> Option<Task<Result<()>>> {
         let worktree = self.worktree_for_entry(entry_id, cx)?;
+        cx.emit(Event::DeletedEntry(worktree.read(cx).id(), entry_id));
         worktree.update(cx, |worktree, cx| {
             worktree.delete_entry(entry_id, trash, cx)
         })
@@ -2204,7 +2205,7 @@ impl Project {
         match event {
             WorktreeStoreEvent::WorktreeAdded(worktree) => {
                 self.on_worktree_added(worktree, cx);
-                cx.emit(Event::WorktreeAdded);
+                cx.emit(Event::WorktreeAdded(worktree.read(cx).id()));
             }
             WorktreeStoreEvent::WorktreeRemoved(_, id) => {
                 cx.emit(Event::WorktreeRemoved(*id));
@@ -2225,23 +2226,25 @@ impl Project {
             }
         }
         cx.observe(worktree, |_, _, cx| cx.notify()).detach();
-        cx.subscribe(worktree, |project, worktree, event, cx| match event {
+        cx.subscribe(worktree, |project, worktree, event, cx| {
+            let worktree_id = worktree.update(cx, |worktree, _| worktree.id());
+            match event {
                 worktree::Event::UpdatedEntries(changes) => {
                     cx.emit(Event::WorktreeUpdatedEntries(
                         worktree.read(cx).id(),
                         changes.clone(),
                     ));
 
-                let worktree_id = worktree.update(cx, |worktree, _| worktree.id());
                     project
                         .client()
                         .telemetry()
                         .report_discovered_project_events(worktree_id, changes);
                 }
                 worktree::Event::UpdatedGitRepositories(_) => {
-                cx.emit(Event::WorktreeUpdatedGitRepositories);
+                    cx.emit(Event::WorktreeUpdatedGitRepositories(worktree_id));
+                }
+                worktree::Event::DeletedEntry(id) => cx.emit(Event::DeletedEntry(worktree_id, *id)),
             }
-            worktree::Event::DeletedEntry(id) => cx.emit(Event::DeletedEntry(*id)),
         })
         .detach();
         cx.notify();

crates/project_panel/src/project_panel.rs

@@ -304,7 +304,7 @@ impl ProjectPanel {
                     cx.notify();
                 }
                 project::Event::WorktreeUpdatedEntries(_, _)
-                | project::Event::WorktreeAdded
+                | project::Event::WorktreeAdded(_)
                 | project::Event::WorktreeOrderChanged => {
                     this.update_visible_entries(None, cx);
                     cx.notify();

crates/semantic_index/src/project_index.rs

@@ -125,7 +125,7 @@ impl ProjectIndex {
         cx: &mut ModelContext<Self>,
     ) {
         match event {
-            project::Event::WorktreeAdded | project::Event::WorktreeRemoved(_) => {
+            project::Event::WorktreeAdded(_) | project::Event::WorktreeRemoved(_) => {
                 self.update_worktree_indices(cx);
             }
             _ => {}

crates/workspace/src/workspace.rs

@@ -810,7 +810,7 @@ impl Workspace {
                     this.collaborator_left(*peer_id, cx);
                 }
 
-                project::Event::WorktreeRemoved(_) | project::Event::WorktreeAdded => {
+                project::Event::WorktreeRemoved(_) | project::Event::WorktreeAdded(_) => {
                     this.update_window_title(cx);
                     this.serialize_workspace(cx);
                 }
@@ -832,7 +832,7 @@ impl Workspace {
                     cx.remove_window();
                 }
 
-                project::Event::DeletedEntry(entry_id) => {
+                project::Event::DeletedEntry(_, entry_id) => {
                     for pane in this.panes.iter() {
                         pane.update(cx, |pane, cx| {
                             pane.handle_deleted_project_item(*entry_id, cx)