Git on main thread (#26573)

This moves spawning of the git subprocess to the main thread. We're not
yet
sure why, but when we spawn a process using GCD's background queues,
sub-processes like git-credential-manager fail to open windows.

This seems to be fixable either by using the main thread, or by using a
standard background thread,
but for now we use the main thread.


Release Notes:

- Git: Fix git-credential-manager

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

crates/git_ui/src/branch_picker.rs

@@ -205,9 +205,9 @@ impl BranchListDelegate {
             return;
         };
         cx.spawn(|_, cx| async move {
-            cx.update(|cx| repo.read(cx).create_branch(&new_branch_name))?
+            cx.update(|cx| repo.read(cx).create_branch(new_branch_name.to_string()))?
                 .await??;
-            cx.update(|cx| repo.read(cx).change_branch(&new_branch_name))?
+            cx.update(|cx| repo.read(cx).change_branch(new_branch_name.to_string()))?
                 .await??;
             Ok(())
         })
@@ -358,7 +358,7 @@ impl PickerDelegate for BranchListDelegate {
                     let cx = cx.to_async();
 
                     anyhow::Ok(async move {
-                        cx.update(|cx| repo.read(cx).change_branch(&branch.name))?
+                        cx.update(|cx| repo.read(cx).change_branch(branch.name.to_string()))?
                             .await?
                     })
                 })??;