virt-ssh-helper: Improve usage information

Specifically:

  * include non-option argument 'URI' in usage summary;
  * mention that it's an internal tool not meant to be
    called directly;
  * exit earlier if required arguments are absent.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/remote/remote_ssh_helper.c

@@ -369,7 +369,10 @@ int main(int argc, char **argv)
     };
     unsigned int flags;
 
-    context = g_option_context_new("- libvirt socket proxy");
+    context = g_option_context_new("URI - libvirt socket proxy");
+    g_option_context_set_summary(context,
+                                 "Internal tool used to handle connections coming from remote\n"
+                                 "clients. Not intended to be called directly by the user.");
     g_option_context_add_main_entries(context, entries, PACKAGE);
     if (!g_option_context_parse(context, &argc, &argv, &error)) {
         g_printerr(_("option parsing failed: %s\n"), error->message);
@@ -381,6 +384,12 @@ int main(int argc, char **argv)
         exit(EXIT_SUCCESS);
     }
 
+    if (argc != 2) {
+        g_autofree char *help = g_option_context_get_help(context, TRUE, NULL);
+        g_printerr("%s", help);
+        exit(EXIT_FAILURE);
+    }
+
     virSetErrorFunc(NULL, NULL);
     virSetErrorLogPriorityFunc(NULL);
 
@@ -395,11 +404,6 @@ int main(int argc, char **argv)
     /* Initialize the log system */
     virLogSetFromEnv();
 
-    if (argc != 2) {
-        g_printerr("%s: expected a URI\n", argv[0]);
-        exit(EXIT_FAILURE);
-    }
-
     uri_str = argv[1];
     VIR_DEBUG("Using URI %s", uri_str);