misc: replace domain of mercurial ML address by mercurial-scm.org This patch also adds new check-code.py pattern to detect invalid usage of "mercurial@selenic.com". Change for test-convert-tla.t is tested, but similar change for almost same test-convert-baz.t isn't yet tested actually, because I couldn't find out the way to get "GNU Arch baz client". AFAIK, buildbot skips test-convert-baz.t, too. Does anybody have appropriate environment for testing?

commandserver: prevent unlink socket twice This patch changes unixforkingservice so it only calls `self._servicehandler.unlinksocket(self.address)` at most once. This is needed by the next patch.

runtests: check ports on IPv6 address Previously, checkportisavailable only checks ports on the IPv4 address. This patch makes it check IPv6 as well. It'll be useful if "localhost" does not have an IPv4 address, or its IPv4 address does not exist somehow.

zeroconf: fail nicely on IPv6 only system zeroconf only knows how to deal with IPv4; I develop on a system where the only IPv4 address is 127.0.0.1. Teach zeroconf to ignore IPv6 addresses when looking for plausible IPv4 connectivity.

chg: verify XDG_RUNTIME_DIR According to the specification [1], $XDG_RUNTIME_DIR should be ignored unless: The directory MUST be owned by the user, and he MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700. This patch adds a check and ignores it if it does not meet part of the criteria. [1]: https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

check-code: permit functools.reduce