checkapk: add test, fix usage

print --help output to stdout and errors to stderr.

checkapk.in

@@ -17,17 +17,37 @@ fi
 
 
 usage() {
-	cat >&2 <<-__EOF__
+	cat <<-__EOF__
 		$program $program_version - find ABI breakages in package upgrades
-		Usage: $program
+		Usage: $program [-h|--help]
 
 		Run in the directory of a built package.
 
+		Options:
+		  -h, --help  Print this help
+
 	__EOF__
 }
 
+args=$(getopt -o h --long help \
+	-n "$program" -- "$@")
+
+if [ $? -ne 0 ]; then
+	usage >&2
+	exit 2
+fi
+eval set -- "$args"
+while true; do
+	case $1 in
+		-h|--help) usage; exit 0;;
+		--) shift; break;;
+		*) exit 1;; # getopt error
+	esac
+	shift
+done
+
 if [ $# -gt 0 ]; then
-	usage
+	usage >&2
 	exit 2
 fi
 

tests/checkapk_test

@@ -0,0 +1,20 @@
+#!/usr/bin/env atf-sh
+
+. $(atf_get_srcdir)/test_env.sh
+init_tests \
+	checkapk_help \
+	checkapk_invalid_opt
+
+DATADIR=$(atf_get_srcdir)/testdata
+
+checkapk_help_body() {
+	atf_check -s exit:0 \
+		-o match:"Usage:" \
+		checkapk --help
+}
+
+checkapk_invalid_opt_body() {
+	atf_check -s not-exit:0 \
+		-e match:"Usage:" \
+		checkapk --invalid
+}