Backport #28140 by @earl-warren
- Make use of the `form-fetch-action` for the merge button, which will
automatically prevent the action from happening multiple times and show
a nice loading indicator as user feedback while the merge request is
being processed by the server.
- Adjust the merge PR code to JSON response as this is required for the
`form-fetch-action` functionality.
- Resolves https://codeberg.org/forgejo/forgejo/issues/774
- Likely resolves the cause of
https://codeberg.org/forgejo/forgejo/issues/1688#issuecomment-1313044
(cherry picked from commit 4ec64c19507caefff7ddaad722b1b5792b97cc5a)
Co-authored-by: Earl Warren <109468362+earl-warren@users.noreply.github.com>
Co-authored-by: Gusted <postmaster@gusted.xyz>
(cherry picked from commit fbf29f29b5)
70c7ee5475