Support for placeholders in files

[thanpolas]

If we are to unleash the full power of cascading generators, some kind of placeholder functionality should exist.

For. e.g. if i want to create a flavor of the standard webapp generator, i have the ability to include it in my generator. However there is no way to easily change common files, like the Gruntfile.js or the index.html.

Some placeholder functionality should exist so that we can easily and safely inject additional content in common files.

I can also see a need for subtracting parts from common files, for e.g. my Xgenerator does not need the Y task from the Gruntfile or index.

In imagineland this would entail markup in the template files so generators could easily target sections of the files and manipulation of the exposed methods each generator has. The last part is about selecting only few methods from each generator to run instead of having them executed all sequentially.

I am not sure what i am asking here, but i am sure that we need to have a look at this. From what i've seen happening, and what i ended up doing, was keeping complete copies of standard boilerplate in each generator. Boilerplate that i am not happy maintaining (e.g. html5bp) as my focus is on another bp.

[addyosmani]

Right now we're a little strapped on resources, but would be happy to consider something in the form of a pull request for placeholders.

[sindresorhus]

Related #154 #138 #137