Due to -c printing the ini config as expected by imp (i.e. with
passwords), it implies the -p option.

The a flag allows adding an account to the accounts list that will be output by
imp. The c flag prints the list of requested accounts in ini format.

This effectively allows a user to specify both flags in order to add an
account to their existing imp accounts file or use the c flag and a
filter to split their accounts file up.

append can now throw an error -> panic if that's the case