Configure now detects VCS info. Configure now detects Watchman.
We can combine the two so configure can detect if Mercurial
is configured with Watchman enabled.
This commit does two things:
1) collects the Mercurial config so it is available to downstream checks
2) examines the config for presence and state of the fsmonitor
extension
We don't yet do anything with the fsmonitor state. But it should be
useful soon. Also, the return value is kinda wonky. This will almost
certainly be improved as soon as there is an actual consumer.
MozReview-Commit-ID: HyHZ2X8VI0h
--HG--
extra : rebase_source : d245d316cc8a27b2827b7824204549b91465bd34
4d26cc09b2