rev-branch-cache: fix message about overwritten data If there is data at the end we ignore, we should not count them as overwritten. This reveal that we something don't overwrite anything, this will be taken car of in the next changeset.

branchmap-v3: detect invalid headerline and raise error Otherwise, broken cache file would be accept as valid, but empty.

head-revs: merge the two inner_headrevs… variants Now that there is only one method, it does not make sense to have two different "inner" method. This is especially true as we are about to add another parameter to the method. So we clean up before that.

head-revs: move hg-cpython's inner_headrevsfiltered closer to inner_headrevs This is pure code movement, it make a coming changesets significantly clearer.

head-revs: teach the pure indexes about the `headrevs` method Having this computation done at the index level unify the API and remove revlog side complexity. It might also be a front runner of handing more responsability to the index.

head-revs: remove the `headrevsfiltered` method on the index This method is no longer called and can be removed.

head-revs: stop calling headrevsfiltered The `headrevs` method have been accepting filter since Mercurial 3.2¹. I guess we can rely on it for now. (except the Rust extension that just gained this capability, but it has it now)

rust-cpython: also accept the `filteredrevs` argument in index.headrevs The C version have been accepting this argument since Mercurial 3.2, lets align the Rust index here. This will make it possible to simplify the code in later changesets.

branchmap: use the proper experimental name in cacheutil Otherwise they are not properly copied around.

interfaces: introduce and use a protocol class for the `mpatch` module See f2832de2a46c for details when this was done for the `bdiff` module. Two things worth pointing out- 1) The `cffi` module "inherits" the `pure` implementation of `patchedsize()` because of its wildcard import. 2) It's odd that the `mpatchError` lives in both `pure` and `cext` modules. I initially thought to move the exception into the new class, and make the existing class name an alias to the class in the new location, but the exception is created in C code by the `cext` module, so that won't work. I don't think a protocol class is approriate, because there's nothing special about the class to distinguish from any other `Exception`. Fortunately, nobody is catching this exception in core, so we can kick the can down the road.

branching: merge stable into default

tests: provide an alternate fake lock for filesystems without symlink support

tests: disable `worker.backgroundclose` to stabilize a test on Windows TIL that `worker.enabled=0` doesn't prevent these workers from spinning up. At any rate, there's already a whole lot of conditionalized output following `cat client.log`, the placement of the "starting 4 threads for background file closing" message seems unstable, and we don't care about those worker threads here. Preventing the message is better for test maintenance.

tests: fix lock file path mangling in `test-racy-mutations.t` on Windows I guess `$TESTTMP_FORWARD_SLASH` gets translated by MSYS. This was in the `.foo_commit_out` file: sh: C;C:\\MinGW\\msys\\1.0\\Users\\Matt\\AppData\\Local\\Temp\\hgtests.1qc8jmdl\\child2\\test-racy-mutations.t-skip-detection\\waitlock_editor.sh: $ENOENT