Fix git-log-script when HEAD is invalid.

It used 'die' without including git-sh-setup-script; since everything
it uses are subdirectory-aware, instead of including the script to
force it to be run from the top, use echo & exit.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-log-script

 #!/bin/sh
+#
+# Copyright (c) 2005 Linus Torvalds
+#
+
+# This one uses only subdirectory-aware commands, so no need to
+# include sh-setup-script.
+
 revs=$(git-rev-parse --revs-only --no-flags --default HEAD "$@") || exit
-[ "$revs" ] || die "No HEAD ref"
-git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | LESS=-S ${PAGER:-less}
+[ "$revs" ] || {
+	echo >&2 "No HEAD ref"
+	exit 1
+}
+git-rev-list --pretty $(git-rev-parse --default HEAD "$@") |
+LESS=-S ${PAGER:-less}