In some cases zero is desirable in roll results.

I took a quick look at the code, and it seems that zero is never returned as a possible outcome (except for !roll d0 or !roll 3d0 where 0 is the only result).

I would like to try to implement this, but before that some things should be clarified.
What would be the best way to explicitly instruct the !roll command to include zero as one of the possible dice roll outcomes?
A few options come in my mind:

• !roll 1d9,0;
• !roll 1d9 --zero or !roll --zero 1d9, or !roll with-zero 1d9;
• !roll 1d[0-9] or !roll 1d0..9 (this would introduce additional functionality - a possibility to specify an explicit range).

Personally I like the last the most.

I am not completely sure though how well any of these proposed options would comply with the rest of !roll's functionality.