rust-status: expose DifferenceMatcher from Rust to Python

rust-matchers: implement DifferenceMatcher This can be generated by the sparse matcher.

rhg: support "!" syntax for disabling extensions This makes it so that calls in test-log.t do not fall back immediately because of the disabled extension, instead going through the CLI parsing code, which breaks because of invalid UTF-8 in a flag. I *think* clap 3.x+ supports this? I'm not sure, and we have to upgrade the minimum Rust version to use clap 3.x anyway which is out of scope for this series, so let's just kick that can down the road a little bit.

revlog: finer computation of "issnapshot" If the parent had an empty diff, we skip of it to compute a diff against the parent base. This create shorter and simpler chain. However these case could be wrongly detected as snapshot. So we improve the code doing this detection. In practice nobody care as when tried on a copy of mozilla-try and we got the same number of snapshot (1315) in both case. Performance where equivalent.

perf: make perf::bundle compatible down to 5.2 A another small change to make it compatible with a wider set of revision. I did not check compatibility in the python-2 territory yet.

perf: make perf::bundle compatible before 61ba04693d65 A small change to make it compatible with a wider set of revision.

branching: merge stable into default

compare-disco: support for `file` nodes specification This leverage the `nodefromfile` feature in core. This make it possible for callers to no longer pay the subset computation cost (and to make sure the subset is the right one, even when the base repository is different)

compare-disco: move case parsing into its own function This is open the way to the next changeset that will allow to specify a list of heads.

compare-disco: add an option to skip the case If we already know the context, we can save a lot of display space by skipping the case. This also open the way to speedup to the way we specify the subsets. (the code is hacky, but this is a quicky and dirty debug script)

compare-disco: display a header by default This help us to understand the output. (the code is hacky, but this is a quicky and dirty debug script)

compare-disco: prepare for primitive argument parsing We need to be able to configure a couple of things, so lets prepare the code for it. (the code is hacky, but this is a quicky and dirty debug script)

phase-shelve: correct unicode string to honor 'shelve.store=internal' In the case of strip-based shelves, there should be no hidden commit found. That's because shelve.store=internal is necessary but not sufficient to enable phase-based shelves; internal-phase must also be set.

status: include `repo` in template context also for resolved paths The `repo` object needs to be in the templater context when using e.g. `relpath`. It has been missing there since it was the unresolved files were added to the templated output in 07ebb567e8bb.

shelve: remove strip and rely on prior state (issue6735)