Comment 4 for bug 1376597

The difference with innobackupex is that it has a server connection, so it is possible to 'autodetect' the default datadir, which I'm working on right now. The xtrabackup binary does not connect to the server, so it should fail with an error if there is no datadir in my.cnf. I was just clarifying that a fix for this bug should target the latter rather than the former.