Support user-supplied (package) templates

[FMorschel]

From a lot of Flutter issues, and this comment:

flutter/flutter#15279 (comment):

[Support user-supplied project templates for flutter create] is not planned, we'd like to see features like this added to packages on pub instead.

I think we should have a way of telling pub we have templates for our packages and users could then do dart pub create package_name-template_name or something.

And the default could be the example if it is a .dart file.

This would help users to know how we imagined our packages to be consumed, and make basic working examples available for people to mess with is always great for learning the API.

[sigurdm]

I know @jonasfj has been designing something around this, but cannot give an ETA...

I personally think the right approach is to:

• Design templates that apply on top of the flutter create templates, such that they don't need to be adapted when those templates change.
• Then one could have a bin/create.dart script in <package>.
• The instructions for applying the template could then be to run
  • flutter create <foo> && cd foo
  • dart pub add <package>
  • dart run <package>:create