You are over thinking, repository is just a link/bridge between your controller and model and hence controller uses repository class instead of the model directly and in that repository you may declare your methods using the model from there, for example:

<?php namespace GD\Repositories\Category;

interface CategoryInterFace{

    public function all();

    public function getCategoriesWith($with);

    public function find($id);
}

Now implement the interface in the repository class:

<?php namespace GD\Repositories\Category;

use \EloquentCategory as Cat; // the model
class CategoryRepository implements CategoryInterFace {
    public function all()
    {
        return Cat::all();
    }

    public function getCategoriesWith($with)
    {
        return Cat::with($with)->get();
    }

    public function find($id)
    {
        return Cat::find($id):
    }
}

To use it in your controller:

<?php

use GD\Repositories\Category\CategoryInterFace;

class CategoryController extends BaseController {

    public function __construct(CategoryInterFace $category)
    {
        $this->cat = $category;
    }

    public function getCatWith()
    {
        $catsProd = $this->cat->getCategoriesWith('products');
        return $catsProd;
    }

    // use any method from your category
    public function getAll()
    {
        $categories = $this->cat->all();

        return View::make('category.index', compact('categories'));
    }

}

Note: Omitted the IoC binding of the repository because this is not your problem and you know that.

Update: I've written an article here: LARAVEL – USING REPOSITORY PATTERN.