stabletailgraph: implement stable-tail sort This adds the computation of the "stable-tail sort", an incremental node sorting method. It is a stepping stone for the implementation of faster label discovery (for example for obs markers) and more caching.

heptapod: add `.gitattributes` file to improve language detection I am fully aware of the irony.

match: match explicit file using a set The matcher as all the logic to do quick comparison against explicit patterns, however the pattern matcher was shadowing the code using that set and used the compiled regex pattern in all cases, which is quite slow. We restore the usage of the set based matching to boost performance. Building the regexp is still consuming a large amount of time (actually, the majority of the time), which is still silly. Maybe using re2 would help that, but this is a quest for another adventure. Another path to improve this is to have a pattern type dedicated to match the exact path to a file only (not a directory). This pattern could use the set matching only and be skipped in the regex all together. Benchmarks ========== In the following benchmark we are comparing the `hg cat` and `hg files` run time when matching against all files in the repository. They are run: - without the rust extensions - with the standard python engine (so without re2) Performance improvement in this series -------------------------------------- ###### hg files ############################################################### ### mercurial-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 0.230092 seconds prev-changeset: 0.230069 seconds this-changeset: 0.211425 seconds (-8.36%) ### mercurial-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 0.234235 seconds prev-changeset: 0.231165 seconds (-1.38%) this-changeset: 0.212300 seconds (-9.43%) ### pypy-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 0.613567 seconds prev-changeset: 0.616799 seconds this-changeset: 0.510852 seconds (-16.82%) ### pypy-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 0.801880 seconds prev-changeset: 0.616393 seconds (-23.22%) this-changeset: 0.511903 seconds (-36.23%) ### netbeans-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 21.541828 seconds prev-changeset: 21.586773 seconds this-changeset: 13.648347 seconds (-36.76%) ### netbeans-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 172.759857 seconds prev-changeset: 21.908197 seconds (-87.32%) this-changeset: 13.945110 seconds (-91.93%) ### mozilla-central-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 62.474221 seconds prev-changeset: 61.279490 seconds (-1.22%) this-changeset: 29.529469 seconds (-52.40%) ### mozilla-central-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 1364.180218 seconds prev-changeset: 62.473549 seconds (-95.40%) this-changeset: 30.625249 seconds (-97.75%) ###### hg cat ################################################################# ### mercurial-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 0.764407 seconds prev-changeset: 0.763883 seconds this-changeset: 0.737326 seconds (-3.68%) ### mercurial-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 0.768924 seconds prev-changeset: 0.765848 seconds this-changeset: 0.174d0b seconds (-4.44%) ### pypy-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 2.065220 seconds prev-changeset: 2.070498 seconds this-changeset: 1.939482 seconds (-6.08%) ### pypy-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 2.276388 seconds prev-changeset: 2.069197 seconds (-9.15%) this-changeset: 1.931746 seconds (-15.19%) ### netbeans-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 40.967983 seconds prev-changeset: 41.392423 seconds this-changeset: 32.181681 seconds (-22.20%) ### netbeans-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 216.388709 seconds prev-changeset: 41.648689 seconds (-80.88%) this-changeset: 32.580817 seconds (-85.04%) ### mozilla-central-2018-08-01-zstd-sparse-revlog ### sorted base-changeset: 105.228510 seconds prev-changeset: 103.315670 seconds (-1.23%) this-changeset: 69.416118 seconds (-33.64%) ### mozilla-central-2018-08-01-zstd-sparse-revlog ### shuffled base-changeset: 1448.722784 seconds prev-changeset: 104.369358 seconds (-92.80%) this-changeset: 70.554789 seconds (-95.13%) Different way to list the same data with this revision ------------------------------------------------------ ###### hg files ############################################################### ### mercurial-2018-08-01-zstd-sparse-revlog root: 0.119182 seconds glob: 0.120697 seconds (+1.27%) sorted: 0.211425 seconds (+77.40%) shuffled: 0.212300 seconds (+78.13%) ### pypy-2018-08-01-zstd-sparse-revlog root: 0.121986 seconds glob: 0.124822 seconds (+2.32%) sorted: 0.510852 seconds (+318.78%) shuffled: 0.511903 seconds (+319.64%) ### netbeans-2018-08-01-zstd-sparse-revlog root: 0.173984 seconds glob: 0.227203 seconds (+30.59%) sorted: 13.648347 seconds (+7744.59%) shuffled: 13.945110 seconds (+7915.16%) ### mozilla-central-2018-08-01-zstd-sparse-revlog root: 0.366463 seconds glob: 0.491030 seconds (+33.99%) sorted: 29.529469 seconds (+7957.96%) shuffled: 30.625249 seconds (+8256.97%) ###### hg cat ################################################################# ### mercurial-2018-08-01-zstd-sparse-revlog glob: 0.647471 seconds root: 0.643120 seconds shuffled: 0.174d0b seconds (+13.92%) sorted: 0.737326 seconds (+13.88%) ### mozilla-central-2018-08-01-zstd-sparse-revlog glob: 40.596983 seconds root: 40.129136 seconds shuffled: 70.554789 seconds (+73.79%) sorted: 69.416118 seconds (+70.99%) ### netbeans-2018-08-01-zstd-sparse-revlog glob: 18.777924 seconds root: 18.613905 seconds shuffled: 32.580817 seconds (+73.51%) sorted: 32.181681 seconds (+71.38%) ### pypy-2018-08-01-zstd-sparse-revlog glob: 1.555319 seconds root: 1.536534 seconds shuffled: 1.931746 seconds (+24.20%) sorted: 1.939482 seconds (+24.70%)

match: sort patterns before compiling them into a regex While investigating cripping performance for `hg cat` in some context, I discovered that, for large inputs, building a regex from out of order patterns result may result in a *much* slower regex and a much slower associated matcher's performance. So we are now sorting the patterns to help the regex engine. There is more to the story as we rely on regexp more than we should. See the next changeset for details. Benchmarks ========== In the following benchmark we are comparing the `hg cat` and `hg files` run time when matching against the full list of files in the repository. They are run: - without the rust extensions - with the standard python enfine (so without re2) sort vs non-sorted - Before this changeset (3f5137543773) --------------------------------------------------------- ###### hg files ############################################################### ### mercurial-2018-08-01-zstd-sparse-revlog sorted: 0.230092 seconds shuffled: 0.234235 seconds (+1.80%) ### pypy-2018-08-01-zstd-sparse-revlog sorted: 0.613567 seconds shuffled: 0.801880 seconds (+30.69%) ### mozilla-central-2018-08-01-zstd-sparse-revlog sorted: 62.474221 seconds shuffled: 1364.180218 seconds (+2083.59%) ### netbeans-2018-08-01-zstd-sparse-revlog sorted: 21.541828 seconds shuffled: 172.759857 seconds (+701.97%) ###### hg cat ################################################################# ### mercurial-2018-08-01-zstd-sparse-revlog sorted: 0.764407 seconds shuffled: 0.768924 seconds ### pypy-2018-08-01-zstd-sparse-revlog sorted: 2.065220 seconds shuffled: 2.276388 seconds (+10.22%) ### netbeans-2018-08-01-zstd-sparse-revlog sorted: 40.967983 seconds shuffled: 216.388709 seconds (+428.19%) ### mozilla-central-2018-08-01-zstd-sparse-revlog sorted: 105.228510 seconds shuffled: 1448.722784 seconds (+1276.74%) sort vs non-sorted - With this changeset ---------------------------------------- ###### hg files ############################################################### ### mercurial-2018-08-01-zstd-sparse-revlog all-list-pattern-sorted: 0.230069 all-list-pattern-shuffled: 0.231165 ### pypy-2018-08-01-zstd-sparse-revlog all-list-pattern-sorted: 0.616799 all-list-pattern-shuffled: 0.616393 ### netbeans-2018-08-01-zstd-sparse-revlog all-list-pattern-sorted: 21.586773 all-list-pattern-shuffled: 21.908197 ### mozilla-central-2018-08-01-zstd-sparse-revlog all-list-pattern-sorted: 61.279490 all-list-pattern-shuffled: 62.473549 ###### hg cat ################################################################# ### mercurial-2018-08-01-zstd-sparse-revlog sorted: 0.763883 seconds shuffled: 0.765848 seconds ### pypy-2018-08-01-zstd-sparse-revlog sorted: 2.070498 seconds shuffled: 2.069197 seconds ### netbeans-2018-08-01-zstd-sparse-revlog sorted: 41.392423 seconds shuffled: 41.648689 seconds ### mozilla-central-2018-08-01-zstd-sparse-revlog sorted: 103.315670 seconds shuffled: 104.369358 seconds

peer: rename makepeer() → _make_peer() In httppeer and sshpeer, there previously were makepeer() and make_peer(), which was confusing. Therefore, this changeset renames one of the functions. makepeer() was the internal function called by make_peer() and some debug command. This function is renamed to _make_peer().

rust: configure MSRV in Clippy This setting makes Clippy never apply lints that are meant for later versions. In case the target precise toolchain is the one running, it does not make a difference, but this gives us a machine-parseable specification that is pretty standard. The README and `hg help rust` are updated to state that `clippy.toml` is the single source of truth about that, also lifting a minor ambiguity: it is fine if the MSRV is lagging behind the version in Debian testing.

rust-readme: mentioned that format check is enforced by CI

rust-readme: mentioning clippy especially since there is a CI check for it.

rust-readme: rst fixes

chg: populate CHGHG if not set Normally, chg determines which `hg` executable to use by first consulting the `$CHGHG` and `$HG` environment variables, and if neither are present defaults to the `hg` found in the user's `$PATH`. If built with the `HGPATHREL` compiler flag, chg will instead assume that there exists an `hg` executable in the same directory as the `chg` binary and attempt to use that. This can cause problems in situations where there are multiple actively-used Mercurial installations on the same system. When a `chg` client connects to a running command server, the server process performs some basic validation to determine whether a new command server needs to be spawned. These checks include things like checking certain "sensitive" environment variables and config sections, as well as checking whether the mtime of the extensions, hg's `__version__.py` module, and the Python interpreter have changed. Crucially, the command server doesn't explicitly check whether the executable it is running from matches the executable that the `chg` client would have otherwise invoked had there been no existing command server process. Without `HGPATHREL`, this still gets implicitly checked during the validation step, because the only way to specify an alternate hg executable (apart from `$PATH`) is via the `$CHGHG` and `$HG` environment variables, both of which are checked. With `HGPATHREL`, however, the command server has no way of knowing which hg executable the client would have run. This means that a client located at `/version_B/bin/chg` will happily connect to a command server running `/version_A/bin/hg` instead of `/version_B/bin/hg` as expected. A simple solution is to have the client set `$CHGHG` itself, which then allows the command server's environment validation to work as intended. I have tested this manually using two locally built hg installations and it seems to work with no ill effects. That said, I'm not sure how to write an automated test for this since the `chg` available to the tests isn't even built with the `HGPATHREL` compiler flag to begin with.