Currently when the Flatpak command line prompts the user with a yes or
no question, the user must type "y" or "n" to respond. This commit
changes it so that the prompt can assume "yes" if the user just presses
Enter. In that case the prompt ends in "[Y/n]" rather than "[y/n]". If
there are some operations that are considered dangerous, we can still
require explicit user input on those, but as far as I can tell those
criteria don't apply to any existing prompts.
This behavior of allowing the user to just press Enter is consistent
with how apt works for example.
Note that this is distinct from the "--assume-yes" option we have, since
that won't prompt the user at all when a decision needs to be made.
Closes: #2113
Approved by: matthiasclasen
7b1a5c4fb9