For loop syntax changed. Also `orelse` apparently no longer works with
non-optional types, which is reasonable but annoying. The path of
least resistance is to make the flag default type optional to mirror
options/arguments.
The bakery bakes the user context type into an object so that it
doesn't have to be specified over and over again. This ends up being a
nicer way of specifying the CLI parameters, except for the fact that
it requires a slightly odd comptime block construct due to `var` not
working at the top level for some reason (and `comptime var` also not
working).