filelog: drop the CamelCase name for `filelog.filelog` See 61557734c0ae for the reasoning.

revlog: drop the CamelCase name for `revlog.revlogproblem` See 61557734c0ae for the reasoning.

revlog: drop the CamelCase name for `revlog.revlogrevisiondelta` These CamelCase names popped up this cycle because pytype was getting confused by the zope decorator, and so the decoration was decoupled from the class declaration. We're in the process of switching all of the zope interfaces to `typing.Protocol` classes, but we're up against the code freeze. It would be nice to use CamelCase for protocol classes (or classes in general), but let's reset to a consistent state and buy some more time to think about this. Since we're moving to Protocol classes and I disabled the interface tests back in ef7d85089952, I'm not bothering to re-add the decorator, and re-confuse pytype. But do place the interface next to the class, so that these places can be found with the `grep` when the time comes to subclass.

tests: use pyflakes as a tool, not a python module The usage of pyflakes as a Python module was introduced in e397c6d74652, to work around issue between Python 2 and Python 3. This issues are long behind us now and we can get beck to using pyflakes as a tool, giving us more flexibility about how we install it. The `hghave` requirements is modified to check that we have a tool available, instead of a python module.

clang-format: do not accept version above 19.x This gives me different formatting on latest version available in Debian. So disabling for now.

rust-update: add a config item to disable the Rust update fastpath Explanations inline.

update: add a Rust fast-path when updating from null (and clean) This case is easy to detect and we have all we need to generate a valid working copy and dirstate entirely in Rust, which speeds things up considerably: On my machine updating a repo of ~300k files goes from 10.00s down to 4.2s, all while consuming 50% less system time, with all caches hot. Something to note is that further improvements will probably happen with the upcoming `InnerRevlog` series that does smarter mmap hanlding, especially for filelogs. Here are benchmark numbers on a machine with only 4 cores (and no SMT enabled) ``` ### data-env-vars.name = heptapod-public-2024-03-25-ds2-pnm # benchmark.name = hg.command.update # bin-env-vars.hg.py-re2-module = default # bin-env-vars.hg.changeset.node = <this change> # benchmark.variants.atomic-update = no # benchmark.variants.scenario = null-to-tip # benchmark.variants.worker = default default: 5.328762 ~~~~~ rust: 1.308654 (-75.44%, -4.02) ### data-env-vars.name = mercurial-devel-2024-03-22-ds2-pnm # benchmark.name = hg.command.update # bin-env-vars.hg.py-re2-module = default # bin-env-vars.hg.changeset.node = <this change> # benchmark.variants.atomic-update = no # benchmark.variants.scenario = null-to-tip # benchmark.variants.worker = default default: 1.693271 ~~~~~ rust: 1.151053 (-32.02%, -0.54) ### data-env-vars.name = mozilla-unified-2024-03-22-ds2-pnm # benchmark.name = hg.command.update # bin-env-vars.hg.py-re2-module = default # bin-env-vars.hg.changeset.node = <this change> # benchmark.variants.atomic-update = no # benchmark.variants.scenario = null-to-tip # benchmark.variants.worker = default default: 38.901613 ~~~~~ rust: 11.637880 (-70.08%, -27.26) ### data-env-vars.name = netbsd-xsrc-public-2024-09-19-ds2-pnm # benchmark.name = hg.command.update # bin-env-vars.hg.py-re2-module = default # bin-env-vars.hg.changeset.node = <this change> # benchmark.variants.atomic-update = no # benchmark.variants.scenario = null-to-tip # benchmark.variants.worker = default default: 4.793727 ~~~~~ rust: 1.505905 (-68.59%, -3.29) ```

merge: improve working-copy mtime race handling Explanations inline. This also makes use of `make_mtime_reliable`, which unifies our mtime raciness logic from the status. On top of this, this fixes the handling of the pure dirstate status to better catch racy status, as we've been doing in Rust for a long time now.

merge: move the filtering of ambiguous files to a dedicated function I have multiple reasons: - The body of `_update` is way too long - This adds typing which will help our tooling and brains understand this code more easily - This function will get more nested and complex in the next patch I've taken the liberty of rewrapping and typo-passing the docstring.

timestamp: make the reliable comparison more usable from outside This is going to be used with pre-computed times unlike in status.