Sync with private repo: removing legacy, minor fix

* for vim highlight: GIT_DIR and GIT_ROOT assignments now have a space
  before a closing bracket;
* DIR_PLACEHOLDER_FILE no longer needed as all metafs files are now
  stored on the same level with % (percent) replacing path separator;
* use full-line (-x) grep option when looking for a file in the
  versioned files list to avoid matching partial filenames.