Fix tests and apply comments from D64604922

Summary:
Some tests were already flaky, so they didn't run in D64604922.

This fixes the tests and also updates the message displayed to users when pushing to push-redirected repos.

I'll work on the branch integration test later, because D64604922 is a significant change that breaks assumptions we had in the beginning.

Reviewed By: RajivTS

Differential Revision: D64677369

fbshipit-source-id: 5f0606ce2bd4586a632ee1a8835e6315a44411eb

eden/mononoke/git_server/src/service/bookmark_mover.rs

@@ -176,7 +176,7 @@ async fn set_ref_inner(
     // Check if push redirector is enabled, if it is then reject the push
     if push_redirector_enabled(&ctx, repo.clone()).await? {
         return Err(anyhow::anyhow!(
-            "Pushes to repo {} are disallowed because its source of truth has been migrated",
+            "Pushes to repo {0} are disallowed because its source of truth has been moved. Use `git pushrebase` or make changes directly in the repo where the source of truth was moved.",
             repo.repo_identity().name()
         ));
     }