working_copy: stop taking initial checkout in constructor

We don't use the value anymore.

lib/src/working_copy.rs

@@ -732,7 +732,6 @@ impl WorkingCopy {
         state_path: PathBuf,
         operation_id: OperationId,
         workspace_id: WorkspaceId,
-        _commit_id: CommitId,
     ) -> WorkingCopy {
         let mut proto = crate::protos::working_copy::Checkout::new();
         proto.operation_id = operation_id.to_bytes();

lib/src/workspace.rs

@@ -69,7 +69,7 @@ fn init_working_copy(
     std::fs::create_dir(&working_copy_state_path).unwrap();
 
     let mut tx = repo.start_transaction(&format!("add workspace '{}'", workspace_id.as_str()));
-    let checkout_commit = tx.mut_repo().check_out(
+    tx.mut_repo().check_out(
         workspace_id.clone(),
         user_settings,
         &repo.store().root_commit(),
@@ -82,7 +82,6 @@ fn init_working_copy(
         working_copy_state_path,
         repo.op_id().clone(),
         workspace_id,
-        checkout_commit.id().clone(),
     );
     (working_copy, repo)
 }