apply: demonstrate a problem applying svn diffs

apply: demonstrate a problem applying svn diffs

Subversion generates diffs that contain funny ---/+++ lines containing
more than just the file names. Example:

	--- a/trunk/README	(revision 4711)
	+++ /dev/null	(nonexistent)

Let's add a test case demonstrating that apply cannot handle the
/dev/null line (although it can handle the trunk/README line just fine).

Reported in https://github.com/git-for-windows/git/issues/1489

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>