Code review comment for lp:~spud/spud/alias

I guess -s would override -a if in doubt. But since this is an assumption that is not clear to the user I think raising an error is preferred.

I agree with s-kramer that any "legal" file name should be allowed.

Just a thought I had the other day: bzr branches (can) have a nickname you can read and set with `bzr nick` (it is automatically set if you `bzr branch`). In case neither -a nor -s are given, diamond could try using the bzr nick to auto-select the alias. In case bzr nick is not available (i.e. you're not running diamond from within a bzr branch) it could go back to the defaults.