hush: in a comment, document what -i might be doing

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -14657,11 +14657,10 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
 	}
  state2:
 	state = 3;
-	if (
+	if (iflag
 #ifndef linux
-	 getuid() == geteuid() && getgid() == getegid() &&
+	 && getuid() == geteuid() && getgid() == getegid()
 #endif
-	 iflag
 	) {
 		const char *shinit = lookupvar("ENV");
 		if (shinit != NULL && *shinit != '\0')

shell/hush.c

@@ -10356,6 +10356,29 @@ int hush_main(int argc, char **argv)
 			/* Well, we cannot just declare interactiveness,
 			 * we have to have some stuff (ctty, etc) */
 			/* G_interactive_fd++; */
+//There are a few cases where bash -i -c 'SCRIPT'
+//has visible effect (differs from bash -c 'SCRIPT'):
+//it ignores TERM:
+//	bash -i -c 'kill $$; echo ALIVE'
+//	ALIVE
+//it resets SIG_INGed HUP to SIG_DFL:
+//	trap '' hup; bash -i -c 'kill -hup $$; echo ALIVE'
+//	Hangup   [the message is not printed by bash, it's the shell which started it]
+//is talkative about jobs and exiting:
+//	bash -i -c 'sleep 1 & exit'
+//	[1] 16170
+//	exit
+//includes $ENV file (only if run as "sh"):
+//	echo last >/tmp/ENV; ENV=/tmp/ENV sh -i -c 'echo HERE'
+//	last: cannot open /var/log/wtmp: No such file or directory
+//	HERE
+//(under "bash", it's the opposite: it runs $BASH_ENV file only *without* -i).
+//
+//ash -i -c 'sleep 3; sleep 3', on ^C, drops into a prompt instead of exiting
+//(this may be a bug, bash does not do this).
+//(ash -i -c 'sleep 3' won't show this, the last command gets auto-"exec"ed)
+//
+//None of the above feel like useful features people would rely on.
 			break;
 		case 's':
 			G.opt_s = 1;