stablerange: rework saving logic to be clearer and safer

obshashrange: rework saving branching to be clearer and safer

sqlcache: protect read query too Some error (like locked database) can even happens when doing readonly operation. So we protect them too. At that point, it seems that pysqlite3 is not the right tool for this job.

sqlite: fast path when nothing to save If we have no new data to save, we should try to do anything. Doing something concurrently is hard enough. If we can avoid doing it at all that would be great.

sqlcache: initialize meta table last It turns out that pysqlite commit after each table creation. This commit is an hopeless attemps to make the caches more concurrent friendly.

obshashrange: always check in base cachekey against the recorded one Ignoring the check in the none case is just disaster waiting to happens.

stablerangecache: fix output in the drifted case The node were not hex, and the field had different order in the pair. This is now fixed.

sqlcache: also ignore integrity error integrity error can happens when multiple client tries to warm similar cache. Given we leave multiple hole in the cache that can be warmed by anyone, this is harder to avoid that we would like. We simply catch the error in this case. Someone will warm the missing entry later.

sqlcache: cache OperationError when saving This is a cache, so we should not crash when trying to operate on it. OperationError can happens when the database is seen as readonly or locked.

sqlcache: passe better connection option These new options should help with handling transaction consistency and database access on high load.

contrib: introduce a small script to stress tests obsolescence exchange Tester have been reporting some error that seems to originate from concurrent access/update to the cache. This script will be useful to reproduce these situations locally.

test-compat: merge mercurial-4.4 into mercurial-4.3

test: adjust glob in previous changeset I forgot to glob the time.

branching: merge with stable

packaging: mark as development version This avoid confusion.

Added tag 8.1.1 for changeset e7abf863e113

packaging: prepare release 8.1.1 Topic is untouched so we keep the previous version number.

branching: merge with stable

test-compat: merge mercurial-4.5 into mercurial-4.4

test-compat: merge mercurial-4.6 into mercurial-4.5

test-compat: merge stable into mercurial-4.6

changelog: add a line about improved prune documentation

changelog: reorder content

prune: more human-friendly documentation The previous help string generally had a highly technical language. I've tried my best to address that.

prune: improve help first line The previous help string for prune didn't mention successors in the first line. Note: Pierre-Yves David changed the original "hidden" to "obsolete" as it is better concept to put forward. (a bit more specific and with more consequence than just "hidden"). We need a good `hg help obsolete/obsolescence` result. We'll try to get this in the next version.

prune: try to clarify the "multi" revisions case I hope this highlight the use case for all three options.

prune: move help about biject after the one about split and fold The --biject flag seems a less common use case.

prune: no longer consider dropping --biject Field testing show it save people one wrong call often enough that it is worth keeping.

prune: more human-friendly documentation for --biject

prune: use ``-s/--succ`` in documentation Extracted by Pierre-Yves David