Modules
Splits mix composer.new argv into APP, REF, the archive's own options
and the recipe flags.
One command of a ComposerNew.Plan: an executable and its arguments,
run in cd (nil for the current directory). label says which part
of the run it is: :create, :install, :record or :run.
Turns mix composer.new argv into the list of commands to run.
The checks mix composer.new makes before it creates anything, and
reports all at once
Parses a mix composer.new recipe reference: COOKBOOK:GROUP/RECIPE,
with an optional @SOURCE naming where the cookbook comes from.
Prints a ComposerNew.Plan, or runs it.
Mix Tasks
Creates an app with igniter.new, installs composer and a cookbook,
records the command line as the first commit, and runs a recipe.