Add an argument to every tested command
@mikael-s suggested to have a mechanism to add an arbitray string, such as
--foo bar, to every command that is tested.
A way to go could be to use a variable, and replace
cmd arg1 arg2 with
cmd $EXTRA arg1 arg2 (with a default empty value for
Perhaps this mechanism could behave like
$EXTRA should not be put when it is already present.