Add support for Luarocks dependencies.

Library/Homebrew/exceptions.rb

@@ -79,6 +79,7 @@ class UnsatisfiedExternalDependencyError < Homebrew::InstallationError
       when :perl then 'cpan'
       when :node then 'npm'
       when :chicken then 'chicken-install'
+      when :lua then "luarocks"
     end
   end
 
@@ -98,6 +99,8 @@ class UnsatisfiedExternalDependencyError < Homebrew::InstallationError
         "npm install"
       when :chicken
         "chicken-install"
+      when :lua
+        "luarocks install"
     end
   end
 end

Library/Homebrew/formula.rb

@@ -745,7 +745,7 @@ EOF
 
     def depends_on name
       @deps ||= []
-      @external_deps ||= {:python => [], :perl => [], :ruby => [], :jruby => [], :chicken => [], :rbx => [], :node => []}
+      @external_deps ||= {:python => [], :perl => [], :ruby => [], :jruby => [], :chicken => [], :rbx => [], :node => [], :lua => []}
 
       case name
       when String, Formula
@@ -753,7 +753,7 @@ EOF
       when Hash
         key, value = name.shift
         case value
-        when :python, :perl, :ruby, :jruby, :chicken, :rbx, :node
+        when :python, :perl, :ruby, :jruby, :chicken, :rbx, :node, :lua
           @external_deps[value] << key
         when :optional, :recommended, :build
           @deps << key

Library/Homebrew/formula_installer.rb

@@ -342,6 +342,7 @@ def external_dep_check dep, type
     when :perl then %W{/usr/bin/env perl -e use\ #{dep}}
     when :chicken then %W{/usr/bin/env csi -e (use #{dep})}
     when :node then %W{/usr/bin/env node -e require('#{dep}');}
+    when :lua then %W{/usr/bin/env luarocks show #{dep}}
   end
 end
 
@@ -365,7 +366,7 @@ class Formula
   end
 
   def check_external_deps
-    [:ruby, :python, :perl, :jruby, :rbx, :chicken, :node].each do |type|
+    [:ruby, :python, :perl, :jruby, :rbx, :chicken, :node, :lua].each do |type|
       self.external_deps[type].each do |dep|
         unless quiet_system(*external_dep_check(dep, type))
           raise UnsatisfiedExternalDependencyError.new(dep, type)