Merge branch 'vd/loose-ref-iteration-optimization'

The code to iterate over loose references have been optimized to reduce the number of lstat() system calls. * vd/loose-ref-iteration-optimization: files-backend.c: avoid stat in 'loose_fill_ref_dir' dir.[ch]: add 'follow_symlink' arg to 'get_dtype' dir.[ch]: expose 'get_dtype' ref-cache.c: fix prefix matching in ref iteration