add svn-diff-head^ script

Signed-off-by: Colin McCabe <cmccabe@alumni.cmu.edu>

diff --git a/svn-diff-head^ b/svn-diff-head^
new file mode 100755 (executable)
index 0000000..decf926
--- /dev/null
+++ b/svn-diff-head^
@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+
+svn diff -r PREV:BASE