### Description An attempt to mirror-sync (`/api/v1/repos/<user>/<repo>/mirror-sync`) a repository that isn't a mirror should probably fail with a `400 (Bad Request)`. Currently Gitea happily answers `200 (OK)` which is an surprising result from a client perspective. ### Gitea Version tip of `main` ### Can you reproduce the bug on the Gitea demo site? No ### Log Gist _No response_ ### Screenshots _No response_ ### Git Version 2.25.1 ### Operating System Ubuntu 20.04 ### How are you running Gitea? Local binary. ### Database PostgreSQL