fsck.fat changes key for "do nothing" action between menus

[Volker Siegel]

The program interacts with the user by a text mode line-by-line interface.
It consists of a sequence of menus, where the choice is made by entering a number.

For context, assume the user starts the program, but intends to make no changes at all.
That could be done by choosing the "No action" option in each menu.

$ sudo fsck /dev/sda1
fsck from util-linux 2.20.1
fsck.fat 3.0.26 (2014-03-07)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
1) Remove dirty bit
2) No action
? 2
There are differences between boot sector and its backup.
This is mostly harmless. Differences: (offset:original/backup)
  65:01/00
1) Copy original to backup
2) Copy backup to original
3) No action
? 3
[ ... ]

After the first menu, I hoped to see a "No action" items in the following menus too, so I can just cancel each action by choosing it with the key 2.
In the next menu, I was happy to see it also has a "No action" item.
But I was very surprised that in the second menu, 2 applies a change! I noticed almost too late.

Now, technically the menus work fine.
But something in the UI design is wrong.

When looking at it like just a normal user interface, I see the following problems here:
 - reassigning the key for a command
 - doing this between two consecutive UI interactions
 - doing this with the most conservative action, used to be on the safe side.
 - doing this in a tool run by root, accessing and changing disks directly.

Proposed solution:
    Use the key 0 for "No action" consistently.
    There is not the usual problem of fixing it breaking an established key map, because of this very bug itself.
    Also, I have seen this elsewhere, it may be even the common way to do it.