I've noticed that under "Actions" there is the "Edit Differential Revisions" that allows you to manage the attached revisions.
This helps a lot for me when the task requires a bit of cleanup.
However, I can't find something similar for git commits. This can help a lot especially if I want to reference and close with a commit that was already pushed to master without any "Fixes TXXXX" keyword. There are probably more scenarios where this would be very helpful.
Maybe "Edit Differential Revisions" can be generalized to manage both Revisions and Git commits for a task?