Git index syncs can back up and cause incidents #12281
Description
As we've seen twice in the last two months — both of which caused pages to go out to the on-call staff member — large numbers of crate publications can cause the Git index sync jobs to back up, since they each require an exclusive lock on the index repo and each sync performs a fetch, commit, and push.
The fix here may be to batch the pending syncs (so fetch once, commit many, then push once), but we need more data before we can answer that.