cache: create `cache` directory at init time The cache directory will be needed very quickly, so it seems simpler to create it early to make sure it has the same owner and permission than the other directory in the repository.

check-exec: write file in 'wcache' instead of 'cache' Some cache are relevant or affected by the working copy used. So the `.hg/cache` directory is not the best place for them because multiple shared repository can end up fighting over them. To address this issue, we introduce a new 'wcache' directory to host this kind of cache. The first user are the `checkisexec` type file. These files describe property of the working copy and fit the use-case well.

rebase: abort in-mem rebase if there's a dirty merge state In-memory merge uses the on-disk merge state, so we should not allow it run in-memory merge when the merge state is not clean. We should probably not use the on-disk merge state when running in-memory merge, but chaning that is not suitable for the stable branch. Differential Revision: https://phab.mercurial-scm.org/D5357

rebase: preserve working copy when redoing in-mem rebase on disk When in-memory rebase runs into conflicts, we retry it on disk. But before we do that, we abort the in-memory rebase. That is done because even though it's mostly in memory, there are still a few state files written (e.g. the merge state). We should make it not write those files so we don't need to abort, but for the stable branch, let's explicitly clear the state we need to clear instead of running the usual abort code. Differential Revision: https://phab.mercurial-scm.org/D5356

tests: show that in-mem rebase falling back loses state Both working copy changes and the merge state is lost when in-memory rebase falls back to on-disk mode. Differential Revision: https://phab.mercurial-scm.org/D5355

commandserver: get around ETIMEDOUT raised by selectors2 selector.select() should exits with an empty event list on timed out, but selectors2 raises OSError if timeout expires while recovering from EINTR. Spotted while debugging new chg feature.

selectors2: backport minimal fix of timeout handling from 2.0.1 The original code would raise TypeError since OSError() doesn't support keyword arguments. We can't simply import the selectors 2.0.1, which still spawns "uname -p" through platform.system(). We could switch to the unreleased version, but I decided to not right now to minimize the change.

mmapindex: set default to 1MB mmapping index is more efficient if we only need a small part of it. The 1MB value has been picked arbitrarily, a lower value might be better. On a large repository with a 60MB index, we see the following performance gain: hg perfindex before: ! wall 0.032023 comb 0.040000 user 0.000000 sys 0.040000 (best of 100) after: ! wall 0.000196 comb 0.000000 user 0.000000 sys 0.000000 (best of 1060) The speed boost benefit all cases, including the one where the full index needs to be parsed. hg perfindex --rev 0 before: ! wall 0.040673 comb 0.030000 user 0.000000 sys 0.030000 (best of 100) after ! wall 0.010713 comb 0.020000 user 0.010000 sys 0.010000 (best of 212) This gain reflect in higher level operation: hg perfbookmarks --clear-revlogs before: ! wall 0.161339 comb 0.160000 user 0.130000 sys 0.030000 (best of 56) after: ! wall 0.123228 comb 0.120000 user 0.120000 sys 0.000000 (best of 68)

mmapindex: move the 'mmapindexthreshold' option out of experimental The option is useful and should be advertised more. We move it out of experimental as a first step. The `storage` section is selected as this is related to how the storage is accessed. A new 'performance' section might be more appropriate. We move from 'mmapindexthreshold` to `mmap-threshold` as non-index item are also suitable for mmap (eg: the rev-branch-cache). If relevant, we can introduce sub-option `mmap-threshold.revlog-index` later.

perf: add a --rev attribute to perfindex This allow for benchmarking the time necessary to look for other version than the tip.