githooks: add Change-Id commit-msg hook

This adds a randomly generated Change-Id to every commit message that
doesn't have one yet.

Change-Id: Ic0d1bb74dc60633cd70550e0dde6b0b8340c89bd

1 files changed, 9 insertions, 0 deletions

diff --git a/githooks/commit-msg b/githooks/commit-msg
new file mode 100755
index 0000000..d241f2b
--- /dev/null
+++ b/githooks/commit-msg
@@ -0,0 +1,9 @@
+#! /usr/bin/env bash
+set -euo pipefail
+change_id=$(head -c32 /dev/urandom | git hash-object --stdin)
+
+git interpret-trailers \
+    --if-exists doNothing \
+    --trailer "Change-Id:I$change_id" \
+    "$1" > "$1.tmp"
+mv "$1.tmp" "$1"