Rework shared commit editors (#24274)

Rework of https://github.com/zed-industries/zed/pull/24130
Uses
1033c0b57e
`COMMIT_EDITMSG` language-related definitions (thanks @d1y )

Instead of using real `.git/COMMIT_EDITMSG` file, create a buffer
without FS representation, stored in the `Repository` and shared the
regular way via the `BufferStore`.
Adds a knowledge of what `Git Commit` language is, and uses it in the
buffers which are rendered in the git panel.


Release Notes:

- N/A

---------

Co-authored-by: Conrad Irwin <conrad@zed.dev>
Co-authored-by: d1y <chenhonzhou@gmail.com>
Co-authored-by: Smit <smit@zed.dev>

crates/git_ui/src/repository_selector.rs

@@ -4,7 +4,7 @@ use gpui::{
 };
 use picker::{Picker, PickerDelegate};
 use project::{
-    git::{GitState, RepositoryHandle},
+    git::{GitState, Repository},
     Project,
 };
 use std::sync::Arc;
@@ -117,13 +117,13 @@ impl<T: PopoverTrigger> RenderOnce for RepositorySelectorPopoverMenu<T> {
 pub struct RepositorySelectorDelegate {
     project: WeakEntity<Project>,
     repository_selector: WeakEntity<RepositorySelector>,
-    repository_entries: Vec<RepositoryHandle>,
-    filtered_repositories: Vec<RepositoryHandle>,
+    repository_entries: Vec<Entity<Repository>>,
+    filtered_repositories: Vec<Entity<Repository>>,
     selected_index: usize,
 }
 
 impl RepositorySelectorDelegate {
-    pub fn update_repository_entries(&mut self, all_repositories: Vec<RepositoryHandle>) {
+    pub fn update_repository_entries(&mut self, all_repositories: Vec<Entity<Repository>>) {
         self.repository_entries = all_repositories.clone();
         self.filtered_repositories = all_repositories;
         self.selected_index = 0;
@@ -194,7 +194,7 @@ impl PickerDelegate for RepositorySelectorDelegate {
         let Some(selected_repo) = self.filtered_repositories.get(self.selected_index) else {
             return;
         };
-        selected_repo.activate(cx);
+        selected_repo.update(cx, |selected_repo, cx| selected_repo.activate(cx));
         self.dismissed(window, cx);
     }
 
@@ -222,7 +222,7 @@ impl PickerDelegate for RepositorySelectorDelegate {
     ) -> Option<Self::ListItem> {
         let project = self.project.upgrade()?;
         let repo_info = self.filtered_repositories.get(ix)?;
-        let display_name = repo_info.display_name(project.read(cx), cx);
+        let display_name = repo_info.read(cx).display_name(project.read(cx), cx);
         // TODO: Implement repository item rendering
         Some(
             ListItem::new(ix)