Add t/perf support for fsmonitor.
* nk/perf-fsmonitor:
t/perf/fsmonitor: add benchmark for dirty status
t/perf/fsmonitor: perf comparison of multiple fsmonitor integrations
t/perf/fsmonitor: initialize test with git reset
t/perf/fsmonitor: factor setup for fsmonitor into function
t/perf/fsmonitor: silence initial git commit
t/perf/fsmonitor: shorten DESC to basename
t/perf/fsmonitor: factor description out for readability
t/perf/fsmonitor: improve error message if typoing hook name
t/perf/fsmonitor: move watchman setup to one-time-repo-setup
t/perf/fsmonitor: separate one time repo initialization