Add a trailing TAB to the "--- filename" lines if there's a space
in the file name. This allows patch(1) to work correctly. The
same is done for diff --nodates.
This was originally suggested by Andrei Vermel, but at the time
I thought git was doing something different.
With this patch, instead of generating N renames, we'll generate
1 rename and N-1 copies.
Ideally the rename should come after the copies instead of before
them, but that'd be harder to do.