discovery: move handling of sampling special case inside sampling function The handling of cases where the number of revisions to sample is smaller than the sample size can be moved with the sample function themselves. This simplifies main logic, preparing a coming refactoring.

discovery: minor fix to some conditionals Since `size` is the upper limit of the sample, we should include it in the check. Otherwize the `more` variable will be zero and the sampling will be useless

delta: reuse _findsnapshot call from previous stage Two different stage of the sparse-revlog logic needs the _findsnapshot data. To avoid recomputing it twice, make it possible to reuse the first computation in the second step. example affected manifest write before: 0.067141s after: 0.064252s (-5%) (total gain since start of series: 95%)

delta: have a native implementation of _findsnapshot The function might traverse a lot of revision, a native implementation get significantly faster. example affected manifest write before: 0.114989 after: 0.067141 (-42%)

transaction: do not overwrite atomic-temp files on error Even though the original files can be restored from the backup, it should be better to not write back a temporary file if we know it can be corrupted.

help: fix typo

rust: use 'impl Trait' in method argument of AncestorsIterator I just didn't know it's stabilized. Let's switch to new convenient syntax. Differential Revision: https://phab.mercurial-scm.org/D5451

rust: use .rev() for reverse range Differential Revision: https://phab.mercurial-scm.org/D5450

histedit: add warning message on editing tagged commits (issue4017) Differential Revision: https://phab.mercurial-scm.org/D5489

strip: extract bookmark movement into a separate function We will need it for the soft-strip case.