Document RUN_SETUP_GENTLY and improve RUN_SETUP docs

Signed-off-by: David Turner <dturner@twitter.com>
After running chdiring to run grep, return to the old directory.

Signed-off-by: David Turner <dturner@twitter.com>
remove str(i?)hash functions from hashmap.c as they are unused

Signed-off-by: David Turner <dturner@twitter.com>
Break out hash-based file integrity checking; optionally use vmac.

vmac isn't really intended for this, but it provides plenty of
integrity checking.  It is also approximately 5 times faster than
SHA-1 on my machine.

Signed-off-by: David Turner <dturner@twitter.com>
Support for filesystem view caching and updating via Facebook's
Watchman daemon.

Signed-off-by: David Turner <dturner@twitter.com>