Merge branch 'av/fsmonitor'

Various fixes to bp/fsmonitor topic.

* av/fsmonitor:
  fsmonitor: simplify determining the git worktree under Windows
  fsmonitor: store fsmonitor bitmap before splitting index
  fsmonitor: read from getcwd(), not the PWD environment variable
  fsmonitor: delay updating state until after split index is merged
  fsmonitor: document GIT_TRACE_FSMONITOR
  fsmonitor: don't bother pretty-printing JSON from watchman
  fsmonitor: set the PWD to the top of the working tree

cache.h

@@ -348,6 +348,7 @@ struct index_state {
 	unsigned char sha1[20];
 	struct untracked_cache *untracked;
 	uint64_t fsmonitor_last_update;
+	struct ewah_bitmap *fsmonitor_dirty;
 };
 
 extern struct index_state the_index;