Merge branch 'cb/clear-quarantine-early-on-all-ref-update-errors'

"receive-pack" checks if it will do any ref updates (various
conditions could reject a push) before received objects are taken
out of the temporary directory used for quarantine purposes, so
that a push that is known-to-fail will not leave crufts that a
future "gc" needs to clean up.

* cb/clear-quarantine-early-on-all-ref-update-errors:
  receive-pack: purge temporary data if no command is ready to run

diff --cc builtin/receive-pack.c
Simple merge

diff --cc t/t5516-fetch-push.sh
Simple merge