ep cli: Clean leftover git locks (#46255)

Sometimes git locks are left over from crashed runs. We now assume
there's only one process of the CLI running and clean them up. If we
want to run multiple processes at the same time, we should consider our
own file-based lock, but it seems fine for an internal tool.

Release Notes:

- N/A

crates/edit_prediction_cli/src/load_project.rs

@@ -204,6 +204,17 @@ async fn setup_worktree(example: &Example, step_progress: &StepProgress) -> Resu
     let worktree_path = repo_name.worktree_path();
     let repo_lock = git::lock_repo(&repo_dir).await;
 
+    // Clean up any stale git lock files from previous crashed runs.
+    // Safe-ish since we have our own lock.
+    // WARNING: Can corrupt worktrees if multiple processes of the CLI are running.
+    let worktree_git_dir = repo_dir
+        .join(".git/worktrees")
+        .join(repo_name.name.as_ref());
+    let index_lock = worktree_git_dir.join("index.lock");
+    if index_lock.exists() {
+        fs::remove_file(&index_lock).ok();
+    }
+
     if !repo_dir.is_dir() {
         step_progress.set_substatus(format!("cloning {}", repo_name.name));
         fs::create_dir_all(&repo_dir)?;