bisect: avoid copying ancestor list for non-merge commits During a bisection, hg needs to compute a list of all ancestors for every candidate commit. This is accomplished via a bottom-up traversal of the set of candidates, during which each revision's ancestor list is populated using the ancestor list of its parent(s). Previously, this involved copying the entire list, which could be very long in if the bisection range was large. To help improve this, we can observe that each candidate commit is visited exactly once, at which point its ancestor list is copied into its children's lists and then dropped. In the case of non-merge commits, a commit's ancestor list consists exactly of its parent's list plus itself. This means that we can trivially reuse the parent's existing list for one of its non-merge children, which avoids copying entirely if that commit is the parent's only child. This makes bisections over linear ranges of commits much faster. During some informal testing in the large publicly-available `mozilla-central` repository, this noticeably sped up bisections over large ranges of history: Setup: $ cd mozilla-central $ hg bisect --reset $ hg bisect --good 0 $ hg log -r tip -T '{rev}\n' 628417 Test: $ time hg bisect --bad tip --noupdate Before: real 3m35.927s user 3m35.553s sys 0m0.319s After: real 1m41.142s user 1m40.810s sys 0m0.285s

packaging: update dulwich to drop the certifi dependency on Windows The presence of `certifi` causes the system certificate store to be ignored, which was reported as a bug against TortoiseHg[1]. It was only pulled in on Windows because of `dulwich`, which was copied from the old TortoiseHg install scripts, in order to support `hg-git`. This version of `dulwich` raises the minimum `urllib3` to a version (1.25) that does certificate verification by default, without the help of `certifi`[2]. We already bundle a newer version of `urllib3`. Note that `certifi` can still be imported from the user site directory, if installed there. But the installer no longer disables the system certificates by default. [1] https://foss.heptapod.net/mercurial/tortoisehg/thg/-/issues/5825 [2] https://github.com/jelmer/dulwich/issues/1025

rhg-status: add support for narrow clones

rust: add support for hints in error messages This will be used by the narrow support code in the next commit.

rust: add Debug constraint to Matcher trait This makes sure we can easily debug which Matcher we're looking at when using trait objects, and is just generally useful. Effort to make the debugging output nicer has been kept to a minimum, please feel free to improve.

tests: fix tar invocation, to address issue 6740

rhg: add sparse support