ac-power: add simple getopt() argument parsing to systemd-ac-power (#8516)

We should probably do that for all our tools, hence fill in this gap
here.

src/ac-power/ac-power.c

@@ -18,19 +18,91 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <getopt.h>
+
 #include "util.h"
 
+static bool arg_verbose = false;
+
+static void help(void) {
+        printf("%s\n\n"
+               "Report whether we are connected to an external power source.\n\n"
+               "  -h --help             Show this help\n"
+               "     --version          Show package version\n"
+               "  -v --verbose          Show state as text\n"
+               , program_invocation_short_name);
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        enum {
+                ARG_VERSION = 0x100,
+        };
+
+        static const struct option options[] = {
+                { "help",    no_argument, NULL, 'h'         },
+                { "version", no_argument, NULL, ARG_VERSION },
+                { "verbose", no_argument, NULL, 'v'         },
+                {}
+        };
+
+        int c;
+
+        assert(argc >= 0);
+        assert(argv);
+
+        while ((c = getopt_long(argc, argv, "hv", options, NULL)) >= 0)
+
+                switch (c) {
+
+                case 'h':
+                        help();
+                        return 0;
+
+                case ARG_VERSION:
+                        return version();
+
+                case 'v':
+                        arg_verbose = true;
+                        break;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        assert_not_reached("Unhandled option");
+                }
+
+        if (optind < argc) {
+                log_error("%s takes no arguments.", program_invocation_short_name);
+                return -EINVAL;
+        }
+
+        return 1;
+}
+
 int main(int argc, char *argv[]) {
         int r;
 
         /* This is mostly intended to be used for scripts which want
          * to detect whether AC power is plugged in or not. */
 
+        log_parse_environment();
+        log_open();
+
+        r = parse_argv(argc, argv);
+        if (r <= 0)
+                goto finish;
+
         r = on_ac_power();
         if (r < 0) {
                 log_error_errno(r, "Failed to read AC status: %m");
-                return EXIT_FAILURE;
+                goto finish;
         }
 
-        return r != 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+        if (arg_verbose)
+                puts(yes_no(r));
+
+finish:
+        return r < 0 ? EXIT_FAILURE : !r;
 }