Diff view (#32922)

Todo:

* [x] Open diffed files as regular buffers
* [x] Update diff when buffers change
* [x] Show diffed filenames in the tab title
* [x] Investigate why syntax highlighting isn't reliably handled for old
text
* [x] remove unstage/restore buttons

Release Notes:

- Adds `zed --diff A B` to show the diff between the two files

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>
Co-authored-by: Agus Zubiaga <agus@zed.dev>

Cargo.lock

@@ -6218,6 +6218,7 @@ dependencies = [
  "ui",
  "unindent",
  "util",
+ "watch",
  "windows 0.61.1",
  "workspace",
  "workspace-hack",

crates/buffer_diff/src/buffer_diff.rs

@@ -1028,7 +1028,11 @@ impl BufferDiff {
         let (base_text_changed, mut changed_range) =
             match (state.base_text_exists, new_state.base_text_exists) {
                 (false, false) => (true, None),
-                (true, true) if state.base_text.remote_id() == new_state.base_text.remote_id() => {
+                (true, true)
+                    if state.base_text.remote_id() == new_state.base_text.remote_id()
+                        && state.base_text.syntax_update_count()
+                            == new_state.base_text.syntax_update_count() =>
+                {
                     (false, new_state.compare(&state, buffer))
                 }
                 _ => (true, Some(text::Anchor::MIN..text::Anchor::MAX)),

crates/cli/src/cli.rs

@@ -13,6 +13,7 @@ pub enum CliRequest {
     Open {
         paths: Vec<String>,
         urls: Vec<String>,
+        diff_paths: Vec<[String; 2]>,
         wait: bool,
         open_new_workspace: Option<bool>,
         env: Option<HashMap<String, String>>,

crates/cli/src/main.rs

@@ -89,6 +89,9 @@ struct Args {
     /// Will attempt to give the correct command to run
     #[arg(long)]
     system_specs: bool,
+    /// Pairs of file paths to diff. Can be specified multiple times.
+    #[arg(long, action = clap::ArgAction::Append, num_args = 2, value_names = ["OLD_PATH", "NEW_PATH"])]
+    diff: Vec<String>,
     /// Uninstall Zed from user system
     #[cfg(all(
         any(target_os = "linux", target_os = "macos"),
@@ -232,9 +235,17 @@ fn main() -> Result<()> {
     let exit_status = Arc::new(Mutex::new(None));
     let mut paths = vec![];
     let mut urls = vec![];
+    let mut diff_paths = vec![];
     let mut stdin_tmp_file: Option<fs::File> = None;
     let mut anonymous_fd_tmp_files = vec![];
 
+    for path in args.diff.chunks(2) {
+        diff_paths.push([
+            parse_path_with_position(&path[0])?,
+            parse_path_with_position(&path[1])?,
+        ]);
+    }
+
     for path in args.paths_with_position.iter() {
         if path.starts_with("zed://")
             || path.starts_with("http://")
@@ -273,6 +284,7 @@ fn main() -> Result<()> {
             tx.send(CliRequest::Open {
                 paths,
                 urls,
+                diff_paths,
                 wait: args.wait,
                 open_new_workspace,
                 env,

crates/git_ui/Cargo.toml

@@ -57,6 +57,7 @@ time.workspace = true
 time_format.workspace = true
 ui.workspace = true
 util.workspace = true
+watch.workspace = true
 workspace-hack.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true

crates/git_ui/src/diff_view.rs

@@ -0,0 +1,497 @@
+//! DiffView provides a UI for displaying differences between two buffers.
+
+use anyhow::Result;
+use buffer_diff::{BufferDiff, BufferDiffSnapshot};
+use editor::{Editor, EditorEvent, MultiBuffer};
+use futures::{FutureExt, select_biased};
+use gpui::{
+    AnyElement, AnyView, App, AppContext as _, AsyncApp, Context, Entity, EventEmitter,
+    FocusHandle, Focusable, IntoElement, Render, Task, Window,
+};
+use language::Buffer;
+use project::Project;
+use std::{
+    any::{Any, TypeId},
+    path::PathBuf,
+    pin::pin,
+    sync::Arc,
+    time::Duration,
+};
+use ui::{Color, Icon, IconName, Label, LabelCommon as _, SharedString};
+use util::paths::PathExt as _;
+use workspace::{
+    Item, ItemHandle as _, ItemNavHistory, ToolbarItemLocation, Workspace,
+    item::{BreadcrumbText, ItemEvent, TabContentParams},
+    searchable::SearchableItemHandle,
+};
+
+pub struct DiffView {
+    editor: Entity<Editor>,
+    old_buffer: Entity<Buffer>,
+    new_buffer: Entity<Buffer>,
+    buffer_changes_tx: watch::Sender<()>,
+    _recalculate_diff_task: Task<Result<()>>,
+}
+
+const RECALCULATE_DIFF_DEBOUNCE: Duration = Duration::from_millis(250);
+
+impl DiffView {
+    pub fn open(
+        old_path: PathBuf,
+        new_path: PathBuf,
+        workspace: &Workspace,
+        window: &mut Window,
+        cx: &mut App,
+    ) -> Task<Result<Entity<Self>>> {
+        let workspace = workspace.weak_handle();
+        window.spawn(cx, async move |cx| {
+            let project = workspace.update(cx, |workspace, _| workspace.project().clone())?;
+            let old_buffer = project
+                .update(cx, |project, cx| project.open_local_buffer(&old_path, cx))?
+                .await?;
+            let new_buffer = project
+                .update(cx, |project, cx| project.open_local_buffer(&new_path, cx))?
+                .await?;
+
+            let buffer_diff = build_buffer_diff(&old_buffer, &new_buffer, cx).await?;
+
+            workspace.update_in(cx, |workspace, window, cx| {
+                let diff_view = cx.new(|cx| {
+                    DiffView::new(
+                        old_buffer,
+                        new_buffer,
+                        buffer_diff,
+                        project.clone(),
+                        window,
+                        cx,
+                    )
+                });
+
+                let pane = workspace.active_pane();
+                pane.update(cx, |pane, cx| {
+                    pane.add_item(Box::new(diff_view.clone()), true, true, None, window, cx);
+                });
+
+                diff_view
+            })
+        })
+    }
+
+    pub fn new(
+        old_buffer: Entity<Buffer>,
+        new_buffer: Entity<Buffer>,
+        diff: Entity<BufferDiff>,
+        project: Entity<Project>,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) -> Self {
+        let multibuffer = cx.new(|cx| {
+            let mut multibuffer = MultiBuffer::singleton(new_buffer.clone(), cx);
+            multibuffer.add_diff(diff.clone(), cx);
+            multibuffer
+        });
+        let editor = cx.new(|cx| {
+            let mut editor =
+                Editor::for_multibuffer(multibuffer.clone(), Some(project.clone()), window, cx);
+            editor.start_temporary_diff_override();
+            editor.disable_inline_diagnostics();
+            editor.set_expand_all_diff_hunks(cx);
+            editor.set_render_diff_hunk_controls(
+                Arc::new(|_, _, _, _, _, _, _, _| gpui::Empty.into_any_element()),
+                cx,
+            );
+            editor
+        });
+
+        let (buffer_changes_tx, mut buffer_changes_rx) = watch::channel(());
+
+        for buffer in [&old_buffer, &new_buffer] {
+            cx.subscribe(buffer, move |this, _, event, _| match event {
+                language::BufferEvent::Edited
+                | language::BufferEvent::LanguageChanged
+                | language::BufferEvent::Reparsed => {
+                    this.buffer_changes_tx.send(()).ok();
+                }
+                _ => {}
+            })
+            .detach();
+        }
+
+        Self {
+            editor,
+            buffer_changes_tx,
+            old_buffer,
+            new_buffer,
+            _recalculate_diff_task: cx.spawn(async move |this, cx| {
+                while let Ok(_) = buffer_changes_rx.recv().await {
+                    loop {
+                        let mut timer = cx
+                            .background_executor()
+                            .timer(RECALCULATE_DIFF_DEBOUNCE)
+                            .fuse();
+                        let mut recv = pin!(buffer_changes_rx.recv().fuse());
+                        select_biased! {
+                            _ = timer => break,
+                            _ = recv => continue,
+                        }
+                    }
+
+                    log::trace!("start recalculating");
+                    let (old_snapshot, new_snapshot) = this.update(cx, |this, cx| {
+                        (
+                            this.old_buffer.read(cx).snapshot(),
+                            this.new_buffer.read(cx).snapshot(),
+                        )
+                    })?;
+                    let diff_snapshot = cx
+                        .update(|cx| {
+                            BufferDiffSnapshot::new_with_base_buffer(
+                                new_snapshot.text.clone(),
+                                Some(old_snapshot.text().into()),
+                                old_snapshot,
+                                cx,
+                            )
+                        })?
+                        .await;
+                    diff.update(cx, |diff, cx| {
+                        diff.set_snapshot(diff_snapshot, &new_snapshot, cx)
+                    })?;
+                    log::trace!("finish recalculating");
+                }
+                Ok(())
+            }),
+        }
+    }
+}
+
+async fn build_buffer_diff(
+    old_buffer: &Entity<Buffer>,
+    new_buffer: &Entity<Buffer>,
+    cx: &mut AsyncApp,
+) -> Result<Entity<BufferDiff>> {
+    let old_buffer_snapshot = old_buffer.read_with(cx, |buffer, _| buffer.snapshot())?;
+    let new_buffer_snapshot = new_buffer.read_with(cx, |buffer, _| buffer.snapshot())?;
+
+    let diff_snapshot = cx
+        .update(|cx| {
+            BufferDiffSnapshot::new_with_base_buffer(
+                new_buffer_snapshot.text.clone(),
+                Some(old_buffer_snapshot.text().into()),
+                old_buffer_snapshot,
+                cx,
+            )
+        })?
+        .await;
+
+    cx.new(|cx| {
+        let mut diff = BufferDiff::new(&new_buffer_snapshot.text, cx);
+        diff.set_snapshot(diff_snapshot, &new_buffer_snapshot.text, cx);
+        diff
+    })
+}
+
+impl EventEmitter<EditorEvent> for DiffView {}
+
+impl Focusable for DiffView {
+    fn focus_handle(&self, cx: &App) -> FocusHandle {
+        self.editor.focus_handle(cx)
+    }
+}
+
+impl Item for DiffView {
+    type Event = EditorEvent;
+
+    fn tab_icon(&self, _window: &Window, _cx: &App) -> Option<Icon> {
+        Some(Icon::new(IconName::Diff).color(Color::Muted))
+    }
+
+    fn tab_content(&self, params: TabContentParams, _window: &Window, cx: &App) -> AnyElement {
+        Label::new(self.tab_content_text(params.detail.unwrap_or_default(), cx))
+            .color(if params.selected {
+                Color::Default
+            } else {
+                Color::Muted
+            })
+            .into_any_element()
+    }
+
+    fn tab_content_text(&self, _detail: usize, cx: &App) -> SharedString {
+        let old_filename = self
+            .old_buffer
+            .read(cx)
+            .file()
+            .and_then(|file| {
+                Some(
+                    file.full_path(cx)
+                        .file_name()?
+                        .to_string_lossy()
+                        .to_string(),
+                )
+            })
+            .unwrap_or_else(|| "untitled".into());
+        let new_filename = self
+            .new_buffer
+            .read(cx)
+            .file()
+            .and_then(|file| {
+                Some(
+                    file.full_path(cx)
+                        .file_name()?
+                        .to_string_lossy()
+                        .to_string(),
+                )
+            })
+            .unwrap_or_else(|| "untitled".into());
+        format!("{old_filename} ↔ {new_filename}").into()
+    }
+
+    fn tab_tooltip_text(&self, cx: &App) -> Option<ui::SharedString> {
+        let old_path = self
+            .old_buffer
+            .read(cx)
+            .file()
+            .map(|file| file.full_path(cx).compact().to_string_lossy().to_string())
+            .unwrap_or_else(|| "untitled".into());
+        let new_path = self
+            .new_buffer
+            .read(cx)
+            .file()
+            .map(|file| file.full_path(cx).compact().to_string_lossy().to_string())
+            .unwrap_or_else(|| "untitled".into());
+        Some(format!("{old_path} ↔ {new_path}").into())
+    }
+
+    fn to_item_events(event: &EditorEvent, f: impl FnMut(ItemEvent)) {
+        Editor::to_item_events(event, f)
+    }
+
+    fn telemetry_event_text(&self) -> Option<&'static str> {
+        Some("Diff View Opened")
+    }
+
+    fn deactivated(&mut self, window: &mut Window, cx: &mut Context<Self>) {
+        self.editor
+            .update(cx, |editor, cx| editor.deactivated(window, cx));
+    }
+
+    fn is_singleton(&self, _: &App) -> bool {
+        false
+    }
+
+    fn act_as_type<'a>(
+        &'a self,
+        type_id: TypeId,
+        self_handle: &'a Entity<Self>,
+        _: &'a App,
+    ) -> Option<AnyView> {
+        if type_id == TypeId::of::<Self>() {
+            Some(self_handle.to_any())
+        } else if type_id == TypeId::of::<Editor>() {
+            Some(self.editor.to_any())
+        } else {
+            None
+        }
+    }
+
+    fn as_searchable(&self, _: &Entity<Self>) -> Option<Box<dyn SearchableItemHandle>> {
+        Some(Box::new(self.editor.clone()))
+    }
+
+    fn for_each_project_item(
+        &self,
+        cx: &App,
+        f: &mut dyn FnMut(gpui::EntityId, &dyn project::ProjectItem),
+    ) {
+        self.editor.for_each_project_item(cx, f)
+    }
+
+    fn set_nav_history(
+        &mut self,
+        nav_history: ItemNavHistory,
+        _: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        self.editor.update(cx, |editor, _| {
+            editor.set_nav_history(Some(nav_history));
+        });
+    }
+
+    fn navigate(
+        &mut self,
+        data: Box<dyn Any>,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) -> bool {
+        self.editor
+            .update(cx, |editor, cx| editor.navigate(data, window, cx))
+    }
+
+    fn breadcrumb_location(&self, _: &App) -> ToolbarItemLocation {
+        ToolbarItemLocation::PrimaryLeft
+    }
+
+    fn breadcrumbs(&self, theme: &theme::Theme, cx: &App) -> Option<Vec<BreadcrumbText>> {
+        self.editor.breadcrumbs(theme, cx)
+    }
+
+    fn added_to_workspace(
+        &mut self,
+        workspace: &mut Workspace,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        self.editor.update(cx, |editor, cx| {
+            editor.added_to_workspace(workspace, window, cx)
+        });
+    }
+}
+
+impl Render for DiffView {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        self.editor.clone()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use editor::test::editor_test_context::assert_state_with_diff;
+    use gpui::TestAppContext;
+    use project::{FakeFs, Fs, Project};
+    use settings::{Settings, SettingsStore};
+    use std::path::PathBuf;
+    use unindent::unindent;
+    use util::path;
+    use workspace::Workspace;
+
+    fn init_test(cx: &mut TestAppContext) {
+        cx.update(|cx| {
+            let settings_store = SettingsStore::test(cx);
+            cx.set_global(settings_store);
+            language::init(cx);
+            Project::init_settings(cx);
+            workspace::init_settings(cx);
+            editor::init_settings(cx);
+            theme::ThemeSettings::register(cx)
+        });
+    }
+
+    #[gpui::test]
+    async fn test_diff_view(cx: &mut TestAppContext) {
+        init_test(cx);
+
+        let fs = FakeFs::new(cx.executor());
+        fs.insert_tree(
+            path!("/test"),
+            serde_json::json!({
+                "old_file.txt": "old line 1\nline 2\nold line 3\nline 4\n",
+                "new_file.txt": "new line 1\nline 2\nnew line 3\nline 4\n"
+            }),
+        )
+        .await;
+
+        let project = Project::test(fs.clone(), ["/test".as_ref()], cx).await;
+
+        let (workspace, mut cx) =
+            cx.add_window_view(|window, cx| Workspace::test_new(project.clone(), window, cx));
+
+        let diff_view = workspace
+            .update_in(cx, |workspace, window, cx| {
+                DiffView::open(
+                    PathBuf::from(path!("/test/old_file.txt")),
+                    PathBuf::from(path!("/test/new_file.txt")),
+                    workspace,
+                    window,
+                    cx,
+                )
+            })
+            .await
+            .unwrap();
+
+        // Verify initial diff
+        assert_state_with_diff(
+            &diff_view.read_with(cx, |diff_view, _| diff_view.editor.clone()),
+            &mut cx,
+            &unindent(
+                "
+                - old line 1
+                + ˇnew line 1
+                  line 2
+                - old line 3
+                + new line 3
+                  line 4
+                ",
+            ),
+        );
+
+        // Modify the new file on disk
+        fs.save(
+            path!("/test/new_file.txt").as_ref(),
+            &unindent(
+                "
+                new line 1
+                line 2
+                new line 3
+                line 4
+                new line 5
+                ",
+            )
+            .into(),
+            Default::default(),
+        )
+        .await
+        .unwrap();
+
+        // The diff now reflects the changes to the new file
+        cx.executor().advance_clock(RECALCULATE_DIFF_DEBOUNCE);
+        assert_state_with_diff(
+            &diff_view.read_with(cx, |diff_view, _| diff_view.editor.clone()),
+            &mut cx,
+            &unindent(
+                "
+                - old line 1
+                + ˇnew line 1
+                  line 2
+                - old line 3
+                + new line 3
+                  line 4
+                + new line 5
+                ",
+            ),
+        );
+
+        // Modify the old file on disk
+        fs.save(
+            path!("/test/old_file.txt").as_ref(),
+            &unindent(
+                "
+                new line 1
+                line 2
+                old line 3
+                line 4
+                ",
+            )
+            .into(),
+            Default::default(),
+        )
+        .await
+        .unwrap();
+
+        // The diff now reflects the changes to the new file
+        cx.executor().advance_clock(RECALCULATE_DIFF_DEBOUNCE);
+        assert_state_with_diff(
+            &diff_view.read_with(cx, |diff_view, _| diff_view.editor.clone()),
+            &mut cx,
+            &unindent(
+                "
+                  ˇnew line 1
+                  line 2
+                - old line 3
+                + new line 3
+                  line 4
+                + new line 5
+                ",
+            ),
+        );
+    }
+}

crates/git_ui/src/git_ui.rs

@@ -22,6 +22,7 @@ mod commit_modal;
 pub mod commit_tooltip;
 mod commit_view;
 mod conflict_view;
+pub mod diff_view;
 pub mod git_panel;
 mod git_panel_settings;
 pub mod onboarding;

crates/language/src/buffer.rs

@@ -4268,6 +4268,11 @@ impl BufferSnapshot {
         self.non_text_state_update_count
     }
 
+    /// An integer version that changes when the buffer's syntax changes.
+    pub fn syntax_update_count(&self) -> usize {
+        self.syntax.update_count()
+    }
+
     /// Returns a snapshot of underlying file.
     pub fn file(&self) -> Option<&Arc<dyn File>> {
         self.file.as_ref()

crates/language/src/syntax_map.rs

@@ -32,6 +32,7 @@ pub struct SyntaxSnapshot {
     parsed_version: clock::Global,
     interpolated_version: clock::Global,
     language_registry_version: usize,
+    update_count: usize,
 }
 
 #[derive(Default)]
@@ -257,7 +258,9 @@ impl SyntaxMap {
     }
 
     pub fn clear(&mut self, text: &BufferSnapshot) {
+        let update_count = self.snapshot.update_count + 1;
         self.snapshot = SyntaxSnapshot::new(text);
+        self.snapshot.update_count = update_count;
     }
 }
 
@@ -268,6 +271,7 @@ impl SyntaxSnapshot {
             parsed_version: clock::Global::default(),
             interpolated_version: clock::Global::default(),
             language_registry_version: 0,
+            update_count: 0,
         }
     }
 
@@ -275,6 +279,10 @@ impl SyntaxSnapshot {
         self.layers.is_empty()
     }
 
+    pub fn update_count(&self) -> usize {
+        self.update_count
+    }
+
     pub fn interpolate(&mut self, text: &BufferSnapshot) {
         let edits = text
             .anchored_edits_since::<(usize, Point)>(&self.interpolated_version)
@@ -443,6 +451,8 @@ impl SyntaxSnapshot {
                 self.language_registry_version = registry.version();
             }
         }
+
+        self.update_count += 1;
     }
 
     fn reparse_with_ranges(

crates/project/src/project.rs

@@ -2439,11 +2439,14 @@ impl Project {
         abs_path: impl AsRef<Path>,
         cx: &mut Context<Self>,
     ) -> Task<Result<Entity<Buffer>>> {
-        if let Some((worktree, relative_path)) = self.find_worktree(abs_path.as_ref(), cx) {
-            self.open_buffer((worktree.read(cx).id(), relative_path), cx)
-        } else {
-            Task::ready(Err(anyhow!("no such path")))
-        }
+        let worktree_task = self.find_or_create_worktree(abs_path.as_ref(), false, cx);
+        cx.spawn(async move |this, cx| {
+            let (worktree, relative_path) = worktree_task.await?;
+            this.update(cx, |this, cx| {
+                this.open_buffer((worktree.read(cx).id(), relative_path), cx)
+            })?
+            .await
+        })
     }
 
     #[cfg(any(test, feature = "test-support"))]

crates/zed/src/main.rs

@@ -46,10 +46,10 @@ use uuid::Uuid;
 use welcome::{BaseKeymap, FIRST_OPEN, show_welcome_view};
 use workspace::{AppState, SerializedWorkspaceLocation, WorkspaceSettings, WorkspaceStore};
 use zed::{
-    OpenListener, OpenRequest, app_menus, build_window_options, derive_paths_with_position,
-    handle_cli_connection, handle_keymap_file_changes, handle_settings_changed,
-    handle_settings_file_changes, initialize_workspace, inline_completion_registry,
-    open_paths_with_positions,
+    OpenListener, OpenRequest, RawOpenRequest, app_menus, build_window_options,
+    derive_paths_with_position, handle_cli_connection, handle_keymap_file_changes,
+    handle_settings_changed, handle_settings_file_changes, initialize_workspace,
+    inline_completion_registry, open_paths_with_positions,
 };
 
 #[cfg(feature = "mimalloc")]
@@ -329,7 +329,12 @@ pub fn main() {
 
     app.on_open_urls({
         let open_listener = open_listener.clone();
-        move |urls| open_listener.open_urls(urls)
+        move |urls| {
+            open_listener.open(RawOpenRequest {
+                urls,
+                diff_paths: Vec::new(),
+            })
+        }
     });
     app.on_reopen(move |cx| {
         if let Some(app_state) = AppState::try_global(cx).and_then(|app_state| app_state.upgrade())
@@ -658,15 +663,21 @@ pub fn main() {
             .filter_map(|arg| parse_url_arg(arg, cx).log_err())
             .collect();
 
-        if !urls.is_empty() {
-            open_listener.open_urls(urls)
+        let diff_paths: Vec<[String; 2]> = args
+            .diff
+            .chunks(2)
+            .map(|chunk| [chunk[0].clone(), chunk[1].clone()])
+            .collect();
+
+        if !urls.is_empty() || !diff_paths.is_empty() {
+            open_listener.open(RawOpenRequest { urls, diff_paths })
         }
 
         match open_rx
             .try_next()
             .ok()
             .flatten()
-            .and_then(|urls| OpenRequest::parse(urls, cx).log_err())
+            .and_then(|request| OpenRequest::parse(request, cx).log_err())
         {
             Some(request) => {
                 handle_open_request(request, app_state.clone(), cx);
@@ -733,13 +744,14 @@ fn handle_open_request(request: OpenRequest, app_state: Arc<AppState>, cx: &mut
     }
 
     let mut task = None;
-    if !request.open_paths.is_empty() {
+    if !request.open_paths.is_empty() || !request.diff_paths.is_empty() {
         let app_state = app_state.clone();
         task = Some(cx.spawn(async move |mut cx| {
             let paths_with_position =
                 derive_paths_with_position(app_state.fs.as_ref(), request.open_paths).await;
             let (_window, results) = open_paths_with_positions(
                 &paths_with_position,
+                &request.diff_paths,
                 app_state,
                 workspace::OpenOptions::default(),
                 &mut cx,
@@ -1027,6 +1039,10 @@ struct Args {
     /// URLs can either be `file://` or `zed://` scheme, or relative to <https://zed.dev>.
     paths_or_urls: Vec<String>,
 
+    /// Pairs of file paths to diff. Can be specified multiple times.
+    #[arg(long, action = clap::ArgAction::Append, num_args = 2, value_names = ["OLD_PATH", "NEW_PATH"])]
+    diff: Vec<String>,
+
     /// Sets a custom directory for all user data (e.g., database, extensions, logs).
     /// This overrides the default platform-specific data directory location.
     /// On macOS, the default is `~/Library/Application Support/Zed`.

crates/zed/src/zed.rs

@@ -570,7 +570,10 @@ fn register_actions(
             window.toggle_fullscreen();
         })
         .register_action(|_, action: &OpenZedUrl, _, cx| {
-            OpenListener::global(cx).open_urls(vec![action.url.clone()])
+            OpenListener::global(cx).open(RawOpenRequest {
+                urls: vec![action.url.clone()],
+                ..Default::default()
+            })
         })
         .register_action(|_, action: &OpenBrowser, _window, cx| cx.open_url(&action.url))
         .register_action(|workspace, _: &workspace::Open, window, cx| {

crates/zed/src/zed/open_listener.rs

@@ -1,6 +1,6 @@
 use crate::handle_open_request;
 use crate::restorable_workspace_locations;
-use anyhow::{Context as _, Result};
+use anyhow::{Context as _, Result, anyhow};
 use cli::{CliRequest, CliResponse, ipc::IpcSender};
 use cli::{IpcHandshake, ipc};
 use client::parse_zed_link;
@@ -12,6 +12,7 @@ use futures::channel::mpsc::{UnboundedReceiver, UnboundedSender};
 use futures::channel::{mpsc, oneshot};
 use futures::future::join_all;
 use futures::{FutureExt, SinkExt, StreamExt};
+use git_ui::diff_view::DiffView;
 use gpui::{App, AsyncApp, Global, WindowHandle};
 use language::Point;
 use recent_projects::{SshSettings, open_ssh_project};
@@ -31,6 +32,7 @@ use workspace::{AppState, OpenOptions, SerializedWorkspaceLocation, Workspace};
 pub struct OpenRequest {
     pub cli_connection: Option<(mpsc::Receiver<CliRequest>, IpcSender<CliResponse>)>,
     pub open_paths: Vec<String>,
+    pub diff_paths: Vec<[String; 2]>,
     pub open_channel_notes: Vec<(u64, Option<String>)>,
     pub join_channel: Option<u64>,
     pub ssh_connection: Option<SshConnectionOptions>,
@@ -38,9 +40,9 @@ pub struct OpenRequest {
 }
 
 impl OpenRequest {
-    pub fn parse(urls: Vec<String>, cx: &App) -> Result<Self> {
+    pub fn parse(request: RawOpenRequest, cx: &App) -> Result<Self> {
         let mut this = Self::default();
-        for url in urls {
+        for url in request.urls {
             if let Some(server_name) = url.strip_prefix("zed-cli://") {
                 this.cli_connection = Some(connect_to_cli(server_name)?);
             } else if let Some(action_index) = url.strip_prefix("zed-dock-action://") {
@@ -61,6 +63,8 @@ impl OpenRequest {
             }
         }
 
+        this.diff_paths = request.diff_paths;
+
         Ok(this)
     }
 
@@ -130,19 +134,25 @@ impl OpenRequest {
 }
 
 #[derive(Clone)]
-pub struct OpenListener(UnboundedSender<Vec<String>>);
+pub struct OpenListener(UnboundedSender<RawOpenRequest>);
+
+#[derive(Default)]
+pub struct RawOpenRequest {
+    pub urls: Vec<String>,
+    pub diff_paths: Vec<[String; 2]>,
+}
 
 impl Global for OpenListener {}
 
 impl OpenListener {
-    pub fn new() -> (Self, UnboundedReceiver<Vec<String>>) {
+    pub fn new() -> (Self, UnboundedReceiver<RawOpenRequest>) {
         let (tx, rx) = mpsc::unbounded();
         (OpenListener(tx), rx)
     }
 
-    pub fn open_urls(&self, urls: Vec<String>) {
+    pub fn open(&self, request: RawOpenRequest) {
         self.0
-            .unbounded_send(urls)
+            .unbounded_send(request)
             .context("no listener for open requests")
             .log_err();
     }
@@ -164,7 +174,10 @@ pub fn listen_for_cli_connections(opener: OpenListener) -> Result<()> {
     thread::spawn(move || {
         let mut buf = [0u8; 1024];
         while let Ok(len) = listener.recv(&mut buf) {
-            opener.open_urls(vec![String::from_utf8_lossy(&buf[..len]).to_string()]);
+            opener.open(RawOpenRequest {
+                urls: vec![String::from_utf8_lossy(&buf[..len]).to_string()],
+                ..Default::default()
+            });
         }
     });
     Ok(())
@@ -201,6 +214,7 @@ fn connect_to_cli(
 
 pub async fn open_paths_with_positions(
     path_positions: &[PathWithPosition],
+    diff_paths: &[[String; 2]],
     app_state: Arc<AppState>,
     open_options: workspace::OpenOptions,
     cx: &mut AsyncApp,
@@ -225,11 +239,27 @@ pub async fn open_paths_with_positions(
         })
         .collect::<Vec<_>>();
 
-    let (workspace, items) = cx
+    let (workspace, mut items) = cx
         .update(|cx| workspace::open_paths(&paths, app_state, open_options, cx))?
         .await?;
 
-    for (item, path) in items.iter().zip(&paths) {
+    for diff_pair in diff_paths {
+        let old_path = Path::new(&diff_pair[0]).canonicalize()?;
+        let new_path = Path::new(&diff_pair[1]).canonicalize()?;
+        if let Ok(diff_view) = workspace.update(cx, |workspace, window, cx| {
+            DiffView::open(old_path, new_path, workspace, window, cx)
+        }) {
+            if let Some(diff_view) = diff_view.await.log_err() {
+                items.push(Some(Ok(Box::new(diff_view))))
+            }
+        }
+    }
+
+    for (item, path) in items.iter_mut().zip(&paths) {
+        if let Some(Err(error)) = item {
+            *error = anyhow!("error opening {path:?}: {error}");
+            continue;
+        }
         let Some(Ok(item)) = item else {
             continue;
         };
@@ -260,14 +290,15 @@ pub async fn handle_cli_connection(
             CliRequest::Open {
                 urls,
                 paths,
+                diff_paths,
                 wait,
                 open_new_workspace,
                 env,
-                user_data_dir: _, // Ignore user_data_dir
+                user_data_dir: _,
             } => {
                 if !urls.is_empty() {
                     cx.update(|cx| {
-                        match OpenRequest::parse(urls, cx) {
+                        match OpenRequest::parse(RawOpenRequest { urls, diff_paths }, cx) {
                             Ok(open_request) => {
                                 handle_open_request(open_request, app_state.clone(), cx);
                                 responses.send(CliResponse::Exit { status: 0 }).log_err();
@@ -288,6 +319,7 @@ pub async fn handle_cli_connection(
 
                 let open_workspace_result = open_workspaces(
                     paths,
+                    diff_paths,
                     open_new_workspace,
                     &responses,
                     wait,
@@ -306,6 +338,7 @@ pub async fn handle_cli_connection(
 
 async fn open_workspaces(
     paths: Vec<String>,
+    diff_paths: Vec<[String; 2]>,
     open_new_workspace: Option<bool>,
     responses: &IpcSender<CliResponse>,
     wait: bool,
@@ -362,6 +395,7 @@ async fn open_workspaces(
 
                     let workspace_failed_to_open = open_local_workspace(
                         workspace_paths,
+                        diff_paths.clone(),
                         open_new_workspace,
                         wait,
                         responses,
@@ -411,6 +445,7 @@ async fn open_workspaces(
 
 async fn open_local_workspace(
     workspace_paths: Vec<String>,
+    diff_paths: Vec<[String; 2]>,
     open_new_workspace: Option<bool>,
     wait: bool,
     responses: &IpcSender<CliResponse>,
@@ -424,6 +459,7 @@ async fn open_local_workspace(
         derive_paths_with_position(app_state.fs.as_ref(), workspace_paths).await;
     match open_paths_with_positions(
         &paths_with_position,
+        &diff_paths,
         app_state.clone(),
         workspace::OpenOptions {
             open_new_workspace,
@@ -437,7 +473,7 @@ async fn open_local_workspace(
         Ok((workspace, items)) => {
             let mut item_release_futures = Vec::new();
 
-            for (item, path) in items.into_iter().zip(&paths_with_position) {
+            for item in items {
                 match item {
                     Some(Ok(item)) => {
                         cx.update(|cx| {
@@ -456,7 +492,7 @@ async fn open_local_workspace(
                     Some(Err(err)) => {
                         responses
                             .send(CliResponse::Stderr {
-                                message: format!("error opening {path:?}: {err}"),
+                                message: err.to_string(),
                             })
                             .log_err();
                         errored = true;
@@ -468,7 +504,7 @@ async fn open_local_workspace(
             if wait {
                 let background = cx.background_executor().clone();
                 let wait = async move {
-                    if paths_with_position.is_empty() {
+                    if paths_with_position.is_empty() && diff_paths.is_empty() {
                         let (done_tx, done_rx) = oneshot::channel();
                         let _subscription = workspace.update(cx, |_, _, cx| {
                             cx.on_release(move |_, _| {
@@ -549,8 +585,16 @@ mod tests {
         cx.update(|cx| {
             SshSettings::register(cx);
         });
-        let request =
-            cx.update(|cx| OpenRequest::parse(vec!["ssh://me@localhost:/".into()], cx).unwrap());
+        let request = cx.update(|cx| {
+            OpenRequest::parse(
+                RawOpenRequest {
+                    urls: vec!["ssh://me@localhost:/".into()],
+                    ..Default::default()
+                },
+                cx,
+            )
+            .unwrap()
+        });
         assert_eq!(
             request.ssh_connection.unwrap(),
             SshConnectionOptions {
@@ -692,6 +736,7 @@ mod tests {
             .spawn(|mut cx| async move {
                 open_local_workspace(
                     workspace_paths,
+                    vec![],
                     open_new_workspace,
                     false,
                     &response_tx,

crates/zed/src/zed/windows_only_instance.rs

@@ -23,7 +23,7 @@ use windows::{
     core::HSTRING,
 };
 
-use crate::{Args, OpenListener};
+use crate::{Args, OpenListener, RawOpenRequest};
 
 pub fn is_first_instance() -> bool {
     unsafe {
@@ -40,7 +40,14 @@ pub fn is_first_instance() -> bool {
 pub fn handle_single_instance(opener: OpenListener, args: &Args, is_first_instance: bool) -> bool {
     if is_first_instance {
         // We are the first instance, listen for messages sent from other instances
-        std::thread::spawn(move || with_pipe(|url| opener.open_urls(vec![url])));
+        std::thread::spawn(move || {
+            with_pipe(|url| {
+                opener.open(RawOpenRequest {
+                    urls: vec![url],
+                    ..Default::default()
+                })
+            })
+        });
     } else if !args.foreground {
         // We are not the first instance, send args to the first instance
         send_args_to_instance(args).log_err();
@@ -109,6 +116,7 @@ fn send_args_to_instance(args: &Args) -> anyhow::Result<()> {
     let request = {
         let mut paths = vec![];
         let mut urls = vec![];
+        let mut diff_paths = vec![];
         for path in args.paths_or_urls.iter() {
             match std::fs::canonicalize(&path) {
                 Ok(path) => paths.push(path.to_string_lossy().to_string()),
@@ -126,9 +134,22 @@ fn send_args_to_instance(args: &Args) -> anyhow::Result<()> {
                 }
             }
         }
+
+        for path in args.diff.chunks(2) {
+            let old = std::fs::canonicalize(&path[0]).log_err();
+            let new = std::fs::canonicalize(&path[1]).log_err();
+            if let Some((old, new)) = old.zip(new) {
+                diff_paths.push([
+                    old.to_string_lossy().to_string(),
+                    new.to_string_lossy().to_string(),
+                ]);
+            }
+        }
+
         CliRequest::Open {
             paths,
             urls,
+            diff_paths,
             wait: false,
             open_new_workspace: None,
             env: None,