localrepo: update branchcache in a more reliable way test-mq-cache.t did apparently look at stale cache content. Testing with different locking mechanism happened to update the cache more frequently and thus caused a test failure.

tests: make qnew in test-mq-caches.t stable The unstable hashes did for other reasons not show up in the test output.

localrepo: remove spurious updatebranchcache return value - it was left over from the refactoring in d01e28657429.

mq: only save dirty files once when savedirty is called multiple times

mq: remove early wlock release in qnew It seems like something that missed the refactoring in 97b734fb9c6f.

mq: use .invalidate to cancel dirty mq state when cancelling transaction Before the code optimistically relied on savedirty not being called a cancelled transaction. If it was called it could save incorrect data. Instead we now start using the invalidate method introduced in b169ba60eebe.

mq: make qsave implementation more explicit It wasn't obvious from the code how qsave mocked around with .hg/patches and .hg/patches.? and what was going on. This makes it more explicit so it will survive future refactorings.

mq: consistently use boolean values for dirty flags

mq: minor cleanup

tag: lock before tagging