Format and test-gmt-dev slash commands not working properly

[weiji14]

Description of the problem

The /format and /test-gmt-dev slash commands added in #646 and #831 respectively seem to have stopped working like they used to, and probably for a while now to be honest. I think GitHub made some changes in regard to bot permissions some time ago (though I can't pin an exact date), and a lot of these tools with auto-commit functionality just broke.

To be specific:

1. For the /format command, an action is triggered and runs to completion, but no formatting commit actually happens. E.g.:

• Add inline example for xyz2grd #1719 (comment)
• Standardize output types for grdhisteq methods #1812 (comment)

2. The /test-gmt-dev command, I think it does run (?), but you have to jump to the 'Actions' tab to see it run which is very inconvenient. From memory, I think there was another problem with how it wasn't testing the changes in the PR branch properly, but some rebased commit instead? E.g.:

• Use Python 3.10 in Continuous Integration tests #1577 (comment)
• Change GMT_IN|GMT_IS_REFERENCE to GMT_IN #517 (comment)

So, we'll either need to update these convenience slash commands, or remove them.

[seisman]

2. The /test-gmt-dev command, I think it does run (?), but you have to jump to the 'Actions' tab to see it run which is very inconvenient.

Possible solution at peter-evans/slash-command-dispatch#87 (comment).

Or we can simply post the run job id (maybe https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}) to the /test-gmt-dev comment.