* lt/dir-cleanup:
Make index preloading check the whole path to the file
Export thread-safe version of 'has_symlink_leading_path()'
Prepare symlink caching for thread-safety
Avoid using 'lstat()' to figure out directories
Avoid doing extra 'lstat()'s for d_type if we have an up-to-date cache entry
Simplify read_directory[_recursive]() arguments
Add 'fill_directory()' helper function for directory traversal