[PATCH] Fixed/Extended example for update hook

Add sample code to distinguish --force rebased head and simple
fast-forward.  At the same time fixes a real bug; the "new ref"
path was using a wrong parameter.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

templates/hooks--update

 #!/bin/sh
 #
 # An example hook script to mail out commit update information.
+# Called by git-receive-pack with arguments: refname sha1-old sha1-new
 #
 # To enable this hook:
 # (1) change the recipient e-mail address
@@ -12,10 +13,15 @@ recipient="commit-list@mydomain.xz"
 if expr "$2" : '0*$' >/dev/null
 then
 	echo "Created a new ref, with the following commits:"
-	git-rev-list --pretty "$2"
+	git-rev-list --pretty "$3"
 else
-	echo "New commits:"
-	git-rev-list --pretty "$3" "^$2"
+	$base=$(git-merge-base "$2" "$3")
+	if [ $base == "$2" ]; then
+		echo "New commits:"
+	else
+		echo "Rebased ref, commits from common ancestor:"
+fi
+git-rev-list --pretty "$3" "^$base"
 fi |
 mail -s "Changes to ref $1" "$recipient"
 exit 0