allow requiring from Gemfile to work

README.md

@@ -18,13 +18,27 @@ And then execute:
 
 ## Usage
 
-Put the following notes in your plugin file (e.g. `lib/guard/myplugin.rb`):
+Put the following in your plugin files (e.g. `lib/guard/myplugin.rb`):
 
 ```ruby
-# Do NOT require "guard/plugin" - it should already required
-# by Guard or by the test helper
+# Don't require "guard/plugin" in hits files
+require 'guard/compat/plugin'
+
+module Guard
+  class MyPlugin < Plugin
+    # (...)
+  end
+end
+
 ```
 
+### IMPORTANT
+
+1) Do not include *any* files from Guard directly (if you need something from Guard which Guard::Compat doesn't provide, file an issue)
+2) include 'guard/compat/plugin' is *all* your files which use `Guard::Plugin`
+3) make sure you include the `< Plugin` part in *every* file which add classes or methods to your plugin class (important if your plugin consists of multiple files/sub class)
+
+
 And in your plugin tests (e.g. `spec/lib/guard/myplugin_spec.rb`):
 
 ```ruby

lib/guard/compat/plugin.rb

@@ -0,0 +1,11 @@
+unless Object.const_defined?('Guard::Plugin')
+  # Provided empty definition so requiring the plugin without Guard won't crash
+  # (e.g. when added to a Gemfile without `require: false`)
+  module Guard
+    class Plugin
+      def initialize
+        fail NotImplementedError
+      end
+    end
+  end
+end

lib/guard/compat/test/helper.rb

@@ -1,4 +1,7 @@
 # Minimal stub allowing a plugin to work
+
+require 'guard/compat/plugin'
+
 module Guard
   class Plugin
     attr_reader :options