vc-diff in vc-dir

[Nick Roberts]

In dired (Emacs 22.1)  you could use vc-diff (v =) on a single file when
other files were marked by placing the cursor over it.  In vc-dir you always
get a diff of the marked files.  Perhaps this is useful also, but quite often
I start to mark files and then want to see what changes I have in other
edited files.  I can no longer do that without visiting the file in a buffer
first.