Make -o/-i arguments mutually exclusive

Right now, it's possible to specify both -o and -i at the same time, which doesn't make any sense.

Also, it's rather non-intuitive that both argument defaults are True and that setting either of them changes their value to False.

I found this issue while working on #34216 (moved), but this issue seemed sufficiently different to justify having its own ticket. I'll post a patch for review in a minute.