chg: document why we send SIGHUP and SIGINT to process group

This makes the code more consistent - other signals are documented.

contrib/chg/procutil.c

@@ -91,11 +91,15 b' void setupsignalhandler(pid_t pid, pid_t'
 
 	struct sigaction sa;
 	memset(&sa, 0, sizeof(sa));
+
+	/* deadly signals meant to be sent to a process group:
+	 * - SIGHUP: usually generated by the kernel, when termination of a
+	 *   process causes that process group to become orphaned
+	 * - SIGINT: usually generated by the terminal */
 	sa.sa_handler = forwardsignaltogroup;
 	sa.sa_flags = SA_RESTART;
 	if (sigemptyset(&sa.sa_mask) < 0)
 		goto error;
-
 	if (sigaction(SIGHUP, &sa, NULL) < 0)
 		goto error;
 	if (sigaction(SIGINT, &sa, NULL) < 0)