Tell Thor to return the right exit code on failure

middleman-core/lib/middleman-core/cli/build.rb

@@ -53,6 +53,9 @@ module Middleman::Cli
     
     # Static methods
     class << self
+      def exit_on_failure?
+        true
+      end
 
       # Middleman::Base singleton
       #

middleman-core/lib/middleman-core/cli/init.rb

@@ -43,6 +43,10 @@ module Middleman::Cli
     end
   end
 
+  def self.exit_on_failure?
+    true
+  end
+  
   # Map "i", "new" and "n" to "init"
   Base.map({
     "i"   => "init",

middleman-core/lib/middleman-core/cli/server.rb

@@ -52,6 +52,10 @@ module Middleman::Cli
     end
   end
 
+  def self.exit_on_failure?
+    true
+  end  
+  
   # Map "s" to "server"
   Base.map({ "s" => "server" })
 end