test-rebuild: display diff output better

test-rebuild

@@ -17,7 +17,7 @@ sudo yum-builddep $PKG.spec
 ARCH=$(arch)
 
 if [ -d $ARCH ]; then
-  echo Please remove $ARCH/
+  echo Please move existing $ARCH/
   exit 1
 fi
 
@@ -37,8 +37,13 @@ for i in $PKGS; do
   for k in list requires provides; do
     rpm -qp --$k $i.rpm | grep -v rpmlib > ../$TMP/$i.$k.test
     rpm -q --$k $i | grep -v rpmlib > ../$TMP/$i.$k.installed
-    diff -u ../$TMP/$i.$k.installed ../$TMP/$i.$k.test > ../$k.$i.diff
-    cat ../$k.$i.diff
+    DIFF=$(diff -u ../$TMP/$i.$k.installed ../$TMP/$i.$k.test)
+    if [ -z "$DIFF" ]; then
+	echo "$i $k: same"
+    else
+	echo $DIFF > ../$k.$i.diff
+	cat ../$k.$i.diff
+    fi
   done
 done