t / t5100 / info0011on commit sha1_file: link() returns -1 on failure, not errno (e32c0a9)
   1Author: A U Thor
   2Email: a.u.thor@example.com
   3Subject: Xyzzy
   4Date: Fri, 8 Aug 2008 13:08:37 +0200 (CEST)
   5