git-gui: Ignore 'No newline at end of file' marker line.

If one or both versions of the file don't have a newline at the end
of the file we get a line telling us so in the diff output.  This
shouldn't be tagged, nor should it generate a warning about not
being tagged.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -706,6 +706,7 @@ proc read_diff {fd} {
 			|| [string match {mode *} $line]
 			|| [string match {new file *} $line]
 			|| [string match {deleted file *} $line]
+			|| $line eq {\ No newline at end of file}
 			|| [regexp {^\* Unmerged path } $line]} {
 			set tags {}
 		} elseif {$is_3way_diff} {