Are you looking for the docs for Jekyll Assets < 2.0.0?

See: https://github.com/jekyll-assets/jekyll-assets/tree/legacy#jekyllassets

Jekyll 3 Assets

Jekyll 3 assets is an asset pipeline using Sprockets 3 to build especially for Jekyll 3. It utilizes new features of both Sprockets and Jekyll to achieve a clean and extensible assets platform for Jekyll.

Configuration

assets:
  cache: false | directory | default: .asset-cache
  cdn: https://cdn.example.com
  skip_prefix_with_cdn: false
  prefix: "/assets"
  assets:
    - "*.png"
    - "bundle.css"
  digest: true
  sources:
    - "_assets/folder"

Asset Digesting

Disable digesting by default in development.
Digest by default in production

You can force digesting with digest: true in your _config.yml

ERB Support

ERB Support is removed in favor of trying to get this included on Github Pages eventually (if I can.) Having ERB presents a security risk to Github because it would allow you to use Ruby in ways they don't want you to.

Tags

stylesheet, css, style
javascript, js
image, img
asset_path

Tag Example:

{% img src magick:2x alt:'This is my alt' %}
{% img src magick:2x alt:'This is my alt' sprockets:accept:image/gif %}

What do the colons mean? Proxies/Tags

argument is a boolean HTML argument.
key:value is an HTML key="value" if no proxy exists.
proxy:key:value will set a proxy key with the given value.
proxy:key is a boolean argument if the proxy and key exists.
unknown:key:value will raise DoubleColonError, escape it.
proxy:unknown:value will raise a UnknownProxyError.

Lets say we have sprockets proxies and sprockets allows you to proxy accept, if you send {% img src sprockets:accept:image/gif } then Sprockets find_asset will get { :accept => "image/gif" } but if you try to proxy "unknown" on sprockets we will raise a Proxy error. For more information then look at parser_spec.rb in the spec folder because it literally lays out the ground rules for our tags as a specification.

Current Proxies:

sprockets:accept:<value> - Tell Sprockets your preferred content type.
sprockets:write_to:<value> - The filename you wish us to write your file to.
magick:resize:<value> - Takes standard ImageMagick resize values.
magick:format:<value> - Takes standard ImageMagick format values.
magick:rotate:<value> - Takes standard ImageMagick resize values.
magick:crop:<value> - Takes standard ImageMagick crop values.
magick:flip:<value> - Takes standard ImageMagick flip values.
magick:2x - Tells us to write a double width/height image.
magick:4x - Tells us to write a quadruple width/height image.
magick:half - Tells us to shrink the image to half.

Filters

There is a full suite of filters, actually, any tag and any proxy can be a filter by way of filter arguments, take the following example:

{{ src | img : "magick:2x" }}

Hooks

:env => [ :pre_init, :post_init ]

You can register and trigger hooks like so:

Jekyll::Assets::Hook.trigger  :env, :post_init
Jekyll::Assets::Hook.register :env, :post_init do
  # Your Work
end

Optional Processing Engines

ES6 Transpiler (through Babel) - add "sprockets-es6" to your Gemfile.
CSS Auto Prefixer - add "autoprefixer-rails" to your Gemfile.

Please note that some of these (if not all) have trouble with Rhino -- therubyrhino so you would probably be best to just use Node.js or io.js at that point rather than trying to fight it.

Engine Settings

Some engines take settings, if they do you can add them like so:

assets:
  engines:
    engine_name:
      option: value

Only whitelisted options are allowed by default, so that we can guard against using paths we don't want to be used. If you wish to have an option whitelisted please file a ticket or submit a pull request.

Plugins where did they go?

They're dead, in the way that they were, use Hooks, they require less patching and give more flexibility to us because we can trigger them every time we have a new environment not just occasionally.

amw/jekyll-assets