Clarify need for absolute paths

Closes #67

README.md

@@ -18,7 +18,7 @@ With Rails 7+, you can start a new application with propshaft using `rails new m
 
 Propshaft makes all the assets from all the paths it's been configured with through `config.assets.paths` available for serving and will copy all of them into `public/assets` when precompiling. This is unlike Sprockets, which did not copy over assets that hadn't been explicitly included in one of the bundled assets. 
 
-You can however exempt directories that have been added through the `config.assets.excluded_paths`. This is useful if you're for example using `app/assets/stylesheets` exclusively as a set of inputs to a compiler like Dart Sass for Rails, and you don't want these input files to be part of the load path.
+You can however exempt directories that have been added through the `config.assets.excluded_paths`. This is useful if you're for example using `app/assets/stylesheets` exclusively as a set of inputs to a compiler like Dart Sass for Rails, and you don't want these input files to be part of the load path. (Remember you need to add full paths, like `Rails.root.join("app/assets/stylesheets")`).
 
 These assets can be referenced through their logical path using the normal helpers like `asset_path`, `image_tag`, `javascript_include_tag`, and all the other asset helper tags. These logical references are automatically converted into digest-aware paths in production when `assets:precompile` has been run (through a JSON mapping file found in `public/assets/.manifest.json`).