D894: fsmonitor: warn when fsmonitor could be used

[quark (Jun Wu)]

quark added inline comments.

INLINE COMMENTS

> krbullock wrote in test-fsmonitor-warning.t:9
> We can't squeeze these into a test that's already set up? Brand-new test cases are discouraged, since so much time in our test suite is already burned on initializing repos.

There was no fsmonitor related tests. So I think this is fine.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D894

To: indygreg, #hg-reviewers, mbthomas, krbullock
Cc: quark, krbullock, mbthomas, mercurial-devel