new .git-revid script for producing revision info

diff --git a/.git-revid b/.git-revid
new file mode 100755 (executable)
index 0000000..c00a29b
--- /dev/null
+++ b/.git-revid
@@ -0,0 +1,4 @@
+#!/bin/bash
+set -e
+set -o pipefail
+git-log -1 --pretty='format:%h %ci %s' HEAD | cut -c1-71