When highlighting a commit, using the context menu over the staged changes
and then selecting "Diff this -> selected" the diff was empty. The same
happened when highlighting the staged changes and using "Diff selected ->
this" over a commit. The reason was a copy/paste error in [diffcmd].
This fixes it.
Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de> Signed-off-by: Paul Mackerras <paulus@samba.org>