Merge branch 'av/fsmonitor'

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