Martin von Zweigbergk <martinvonz@google.com> [Fri, 06 Sep 2019 23:26:30 -0700] rev 42876
check-code: allow command substitution with $(command)
Both `command` and $(command) are specified by POSIX. The latter nests
better. I don't see why we shouldn't allow both (or only the latter).
Differential Revision: https://phab.mercurial-scm.org/D6789