Prototype implementation of dependency resolution (#2)

README.md

@@ -14,6 +14,7 @@ Somewhere between [Pathogen](https://github.com/tpope/vim-pathogen) and
 - Parallel installation/update (requires
   [+ruby](http://junegunn.kr/2013/09/installing-vim-with-ruby-support/))
 - Smallest possible feature set
+- Dependency resolution using `Plugfile` (experimental)
 
 ### Cons.
 
@@ -64,6 +65,34 @@ plugins with `plug#begin(path)` call.
 
 (Default number of threads = `g:plug_threads` or 16)
 
+### Dependency resolution
+
+If a Vim plugin specifies its dependent plugins in `Plugfile` in its root
+directory, vim-plug will automatically source it recursively during the
+installation.
+
+A `Plugfile` should contain a set of `Plug` commands for the dependent plugins.
+
+I've created two dummy repositories with Plugfiles as an example to this scheme.
+
+- [junegunn/dummy1](https://github.com/junegunn/dummy1)
+  - `Plug 'junegunn/vim-scroll-position'`
+  - `Plug 'junegunn/dummy2'`
+- [junegunn/dummy2](https://github.com/junegunn/dummy2)
+  - `Plug 'junegunn/Zenburn'`
+  - `Plug 'junegunn/jellybeans.vim'`
+  - `Plug 'junegunn/dummy1'`
+    - (Circular dependencies are ignored)
+
+If you put `Plug 'junegunn/dummy1'` in your configuration file, and run
+`:PlugInstall`,
+
+1. vim-plug first installs dummy1
+2. And sees if the repository has Plugfile
+3. Plugfile is loaded and vim-plug discovers dependent plugins
+4. Dependent plugins are then installed as well, and their Plugfiles are
+   examined and their dependencies are resolved recursively.
+
 ### Articles
 
 - [Writing my own Vim plugin manager](http://junegunn.kr/2013/09/writing-my-own-vim-plugin-manager)