mq: restore _branchtags() fast path (issue3223) Since a5917346c72e, mq saves the nodeid of the first applied patch to cache/branchheads, which breaks the optimized cache handling introduced in fbf8320f25c8. The problem is the revision being committed is appended to mqrepo.applied after the commit succeeds, which means mqrepo._branchtags() performs a regular update and write the first applied patch to the branch cache. One solution is to set a context variable _committingpatch on the mqrepo while it is committing a patch and to take it in account when deciding to fast-path mqrepo._branchtags(). Not really elegant but it works. The changes to test-mq-caches.t reverse changes introduced by a5917346c72e. The cache should not have been updated with mq records. The changes to test-keyword.t are indirectly caused by a5917346c72e. Reported and analyzed by Yuya Nishihara <yuya@tcha.org> Notes: - qpush still makes a slow path _branchtags() call when checking heads. Maybe this can be optimized. - be careful when merging this patch in default as secretcommit() was renamed newcommit() right after the end of the code freeze.