new file mode 100755
--- /dev/null
+++ b/scripts/move-if-change
@@ -0,0 +1,15 @@
+#!/bin/sh
+#
+# Like mv $1 $2, but if the files are the same, just delete $1.
+# Status is 0 if $2 is changed, 1 otherwise.
+
+if test -r $2; then
+  if cmp $1 $2 > /dev/null; then
+    echo $2 is unchanged
+    rm -f $1
+  else
+    mv -f $1 $2
+  fi
+else
+  mv -f $1 $2
+fi