match: make the FLAG_RE pattern a raw string PyCharm was complaining about invalid escape sequences since this was added recently in 3eda36e9b3d6.

configitems: add a default value for "merge-tools.xxx.regappend" When trying to figure out how `hg help -v` took the Set interpolation path in f09bc2ed9100, I turned on devel warnings and noticed this (unrelated) warning: devel-warn: specifying a mismatched default value for a registered config item: 'merge-tools.beyondcompare4.regappend' '' at: c:\Users\Matt\hg\mercurial\filemerge.py:46 (_toolstr) The previous default value for this config was `None`, but that slightly complicates the code at the only site it is used, referenced above.

attr: vendor 22.1.0 The previous version was 5 years old, and pytype 2022.06.30 started complaining about various uses (e.g. seeing `mercurial.thirdparty.attr._make._CountingAttr` instead of `bytearray`). Hopefully this helps. Additionally, this has official python 3.11 support. The `attrs` package is left out, because it is simply a bunch of *.pyi stubs and `from attr.X import *`, and that's not how they've been used up to this point. We'd probably need to customize those anyway to `from mercurial.thirdparty.attr import *`.

tests: update test-util.py for modern attrs package When updating to 22.1.0, this test started failing: Traceback (most recent call last): File "/tmp/mercurial-ci/tests/test-util.py", line 53, in <module> _start_default = (util.timedcmstats.start.default, 'factory') AttributeError: type object 'timedcmstats' has no attribute 'start' Poking around in `hg debugshell`, the attribute is indeed missing, but looks to be attached to `__attrs_attrs__` in both the currently vendored and the modern version of attrs. The old attrs packages will print the same for both accesses, so fingers crossed... >>> print((util.timedcmstats.start.default, 'factory')) (Factory(factory=<function timedcmstats.<lambda> at 0x000001EFDF0F21F0>, takes_self=False), 'factory') >>> print((util.timedcmstats.__attrs_attrs__.start.default, 'factory')) (Factory(factory=<function timedcmstats.<lambda> at 0x000001EFDF0F21F0>, takes_self=False), 'factory')