xfstests: add a unified diff option

From: Matthew Kent <mkent@magoazul.com>


Add the -udiff option to the test driver to make test output more
easily readable.

[hch:  why not make this default?]


Reviewed-by: Christoph Hellwig <hch@lst.de>

Index: xfs-cmds/xfstests/common
===================================================================
--- xfs-cmds.orig/xfstests/common	2008-12-01 22:06:21.000000000 +0100
+++ xfs-cmds/xfstests/common	2008-12-22 14:06:59.485250140 +0100
@@ -107,6 +107,7 @@ check options
     -nfs                test NFS
     -l			line mode diff (default)
     -xdiff		graphical mode diff
+    -udiff		show unified diff
     -n			show me, do not run tests
     -q			quick [deprecated]
     -T			output timestamps
@@ -157,6 +158,11 @@ testlist options
 	    fi
 	    ;;
 
+	-udiff) # show a unified diff
+	    xpand=false
+	    diff="$diff -u"
+	    ;;
+
 	-q)	# "quick", no longer used - always quick :-)
 	    xpand=false
 	    ;;