git-gui: Don't attempt to tag new file/deleted file headers in diffs.

We don't want to tag these new file/delete file lines, as they aren't
actually that interesting.  Its quite clear from the diff itself that
the file is a new file or is a deleted file (as the entire thing will
appear in the diff).

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

git-gui.sh

@@ -704,6 +704,8 @@ proc read_diff {fd} {
 
 		if {[string match {index *} $line]
 			|| [string match {mode *} $line]
+			|| [string match {new file *} $line]
+			|| [string match {deleted file *} $line]
 			|| [regexp {^\* Unmerged path } $line]} {
 			set tags {}
 		} elseif {$is_3way_diff} {