Allow viewing past commits in Zed (#27636)

This PR adds functionality for loading the diff for an arbitrary git
commit, and displaying it in a tab. To retrieve the diff for the commit,
I'm using a single `git cat-file --batch` invocation to efficiently load
both the old and new versions of each file that was changed in the
commit.

Todo

* Features
* [x] Open the commit view when clicking the most recent commit message
in the commit panel
  * [x] Open the commit view when clicking a SHA in a git blame column
  * [x] Open the commit view when clicking a SHA in a commit tooltip
  * [x] Make it work over RPC
  * [x] Allow buffer search in commit view
* [x] Command palette action to open the commit for the current blame
line
* Styling
* [x] Add a header that shows the author, timestamp, and the full commit
message
  * [x] Remove stage/unstage buttons in commit view
  * [x] Truncate the commit message in the tab
* Bugs
  * [x] Dedup commit tabs within a pane
  * [x] Add a tooltip to the tab

Release Notes:

- Added the ability to show past commits in Zed. You can view the most
recent commit by clicking its message in the commit panel. And when
viewing a git blame, you can show any commit by clicking its sha.

crates/git_ui/src/git_ui.rs

@@ -3,6 +3,7 @@ use std::any::Any;
 use ::settings::Settings;
 use command_palette_hooks::CommandPaletteFilter;
 use commit_modal::CommitModal;
+mod blame_ui;
 use git::{
     repository::{Branch, Upstream, UpstreamTracking, UpstreamTrackingStatus},
     status::{FileStatus, StatusCode, UnmergedStatus, UnmergedStatusCode},
@@ -17,6 +18,8 @@ use workspace::Workspace;
 mod askpass_modal;
 pub mod branch_picker;
 mod commit_modal;
+pub mod commit_tooltip;
+mod commit_view;
 pub mod git_panel;
 mod git_panel_settings;
 pub mod onboarding;
@@ -30,6 +33,8 @@ actions!(git, [ResetOnboarding]);
 pub fn init(cx: &mut App) {
     GitPanelSettings::register(cx);
 
+    editor::set_blame_renderer(blame_ui::GitBlameRenderer, cx);
+
     cx.observe_new(|workspace: &mut Workspace, _, cx| {
         ProjectDiff::register(workspace, cx);
         CommitModal::register(workspace);