carlhuda/janus — pull request #487 by tpope (2012-12-04 00:54:06+00:00)
Title: Don't blow up of ~/.vim/_* is missing

Presumably this only came to light because of a botched setup process,
but Vim absolutely loses its shit if you set `'directory'` or
`'backupdir'` to contain only directories that don't exist. Much safer
to prepend.