git_ui: Branch picker improvements (#26287)

- Truncate branch names based on the width of the picker
- Use a footer for "Create branch" instead of a picker entry

Still to do:

- [x] Select the footer button when no matches and run the create logic
on `enter`
- [x] Make it possible to quickly select the footer button from the
keyboard when there are matches

Release Notes:

- Git Beta: Removed limitation that made it impossible to create a
branch from the branch picker when it too closely resembled an existing
branch name

crates/project/src/git.rs

@@ -636,7 +636,7 @@ impl GitStore {
 
         repository_handle
             .update(&mut cx, |repository_handle, _| {
-                repository_handle.create_branch(branch_name)
+                repository_handle.create_branch(&branch_name)
             })?
             .await??;
 
@@ -656,7 +656,7 @@ impl GitStore {
 
         repository_handle
             .update(&mut cx, |repository_handle, _| {
-                repository_handle.change_branch(branch_name)
+                repository_handle.change_branch(&branch_name)
             })?
             .await??;
 
@@ -1695,7 +1695,8 @@ impl Repository {
         })
     }
 
-    pub fn create_branch(&self, branch_name: String) -> oneshot::Receiver<Result<()>> {
+    pub fn create_branch(&self, branch_name: &str) -> oneshot::Receiver<Result<()>> {
+        let branch_name = branch_name.to_owned();
         self.send_job(|repo| async move {
             match repo {
                 GitRepo::Local(git_repository) => git_repository.create_branch(&branch_name),
@@ -1720,7 +1721,8 @@ impl Repository {
         })
     }
 
-    pub fn change_branch(&self, branch_name: String) -> oneshot::Receiver<Result<()>> {
+    pub fn change_branch(&self, branch_name: &str) -> oneshot::Receiver<Result<()>> {
+        let branch_name = branch_name.to_owned();
         self.send_job(|repo| async move {
             match repo {
                 GitRepo::Local(git_repository) => git_repository.change_branch(&branch_name),