localrepo: handle rename with hardlinks properly In "aftertrans", we rename "journal.*" to "undo.*". We expect "journal.*" files to disappear after renaming. However, if "journal.foo" and "undo.foo" refer to a same file (hardlink), rename may be a no-op, leaving both files on disk, according to Linux manpage [1]: If oldpath and newpath are existing hard links referring to the same file, then rename() does nothing, and returns a suc‐ cess status. The POSIX specification [2] is not very clear about what to do. To be safe, remove "undo.*" before the rename so "journal.*" cannot be left on disk. [1]: http://man7.org/linux/man-pages/man2/rename.2.html [2]: http://pubs.opengroup.org/onlinepubs/9699919799/