call the gerrit commit-msg hook if present

This a a prep-work for if and when we use gerrit
it is very important to call gerrit's commit-msg hook
and the sooner we teach our own hook to play nice with it
the less likely we will have issue during migration

git-hooks/commit-msg

@@ -14,6 +14,8 @@
 
 # This example catches duplicate Signed-off-by lines.
 
+base_dir=$(dirname $0)
+
 abort() {
     cp $1 $1.save
     cat >&2 <<EOF
@@ -59,4 +61,8 @@ if [ -n "`grep '^[[:space:]]\+\*.*:' $1`" -a -z "`grep '^\*' $1`" ] ; then
     abort "$1" "Please don't use whitespace in front of '* file: Description.' entries."
 fi
 
+if [ -f "${base_dir}/gerrit-commit-msg" ] ; then
+    source "${base_dir}/gerrit-commit-msg"
+fi
+
 exit 0