If patch is already applied the apply patch checker should issue a warning.
In this morning's glibc patch review discussion we agreed that if a patch is already applied by the time the pre-commit CI system attemps to apply it the result should be a "warning" at the patch application stage, with a note saying the patch is already applied.
The patch application should be a failure only if it is any other case than the patch is already applied. It is OK for it to be a failure if the patches are different e.g. patch author tweaked the patch.