Performance fix: 'git rev-parse HEAD' is faster than 'git status'.
Use `candidates' field.
We need `volatile' option to properly update matched candidates.
Faster matching.
Performance fix: checking untracked files costs too much.
- Use '-uno' option to exclude untracked files on an update check for
  modified files
- Skip update check for untracked files since 'git status' costs as the
  same as 'git ls-files --others --exclude-standard'
Pass `default-directory' by `anything-attrset'.
Asynchronously retrieve file list.
Set git root directory.
Throttled update.
Check anything window just before update.
Restore line position.
`anything-buffer\' gives a buffer name, not a buffer.
Restoring line position must be done in (anything-window).
Skip noncandidate lines on restoring the line position and update mode line.
Merge pull request #1 from tarao/async

Make 'git ls-files' invocation asynchronous