wireprotoserver: ensure that output stream gets flushed on exception Previously flush was happening due to Python finalizer being run on `BufferedWriter`. With upgrade to Python 3.11 this started randomly failing. My guess is that the finalizer on the raw `FileIO` object may be running before the finalizer of `BufferedWriter` has a chance to run. At any rate, since we're not relying on finalizers in the happy case we should also not rely on them in case of exception.

match: strengthen visit_children_set invariant, Recursive means "all files" My previous interpretation of "Recursive" was too relaxed: I thought it instructed the caller to do something like this: > you can stop calling `visit_children_set` because you'll need to descend into > every directory recursively, but you should still check every file if it > matches or not Whereas the real instruction seems to be: > I guarantee that everything in this subtree matches, you can stop > querying the matcher for all files and dirs altogether. The evidence to support this: - the test actually passes with the stronger invariant, revealing no exceptions from this rule - the implementation of `visit_children_set` for `DifferenceMatcher` clearly relies on this requirement, so it must hold for that not to lead to bugs.

match: fix the rust-side bug in visit_children_set for rootfilesin matchers The fix is checked by `test_pattern_matcher_visit_children_set` test, which is what caught the bug in the first place, but also by an end-to-end test that I made for this purpose. Accept the new results of Cargo tests Many of these were already annotated with "FIXME", which is a good sign.

match: fix the "visitdir" method on "rootfilesin" matchers This fixes just the Python side, the fix for the rust side will follow shortly.

match: rename RootFiles to RootFilesIn for more consistency

match: small tweak to PatternMatcher.visit_children_set This makes it a bit more efficient (avoid a computation in case of early return), and in my opinion clearer.

matchers: fix the bug in rust PatternMatcher that made it cut off early This brings the rust output in line with the Python output.

tests: add an end-to-end test to show a bug in `visit_children_set` Concretely, `rootfilesin` is completely broken with respect to `visit_children_set` optimization.

tests: add tests and document expectations from visit_children_set in rust The tests this patch are adding have the form of formal spec in invariants::visit_children_set::holds, and then a series of checks that all examples must satisfy this formal spec. I tried to make the spec consistent with how this function is used and how it was originally conceived. This is in conflict with how it's documented in Rust. Some of the implementations also fail to implement this spec, which leads to bugs, in particular when complicated patterns are used with `hg status`.

tests: add a test that demonstrates a bug in rhg status pattern handling The bug is in [visit_children_set], will be elaborated on in follow-up changes.