Start recording the formula path in the install receipt

Later we can use this information to try and load the formula from the
correct source.

Library/Homebrew/tab.rb

@@ -11,16 +11,23 @@ class Tab < OpenStruct
   FILENAME = 'INSTALL_RECEIPT.json'
 
   def self.create(formula, compiler, stdlib, build)
-    Tab.new :used_options => build.used_options.as_flags,
-            :unused_options => build.unused_options.as_flags,
-            :tabfile => formula.prefix.join(FILENAME),
-            :built_as_bottle => !!ARGV.build_bottle?,
-            :poured_from_bottle => false,
-            :tapped_from => formula.tap,
-            :time => Time.now.to_i,
-            :HEAD => Homebrew.git_head,
-            :compiler => compiler,
-            :stdlib => stdlib
+    attributes = {
+      :used_options => build.used_options.as_flags,
+      :unused_options => build.unused_options.as_flags,
+      :tabfile => formula.prefix.join(FILENAME),
+      :built_as_bottle => !!ARGV.build_bottle?,
+      :poured_from_bottle => false,
+      :tapped_from => formula.tap,
+      :time => Time.now.to_i,
+      :HEAD => Homebrew.git_head,
+      :compiler => compiler,
+      :stdlib => stdlib,
+      :source => {
+        :path => formula.path.to_s,
+      },
+    }
+
+    new(attributes)
   end
 
   def self.from_file path
@@ -83,15 +90,22 @@ class Tab < OpenStruct
   end
 
   def self.dummy_tab f=nil
-    Tab.new :used_options => [],
-            :unused_options => (f.options.as_flags rescue []),
-            :built_as_bottle => false,
-            :poured_from_bottle => false,
-            :tapped_from => "",
-            :time => nil,
-            :HEAD => nil,
-            :stdlib => nil,
-            :compiler => :clang
+    attributes = {
+      :used_options => [],
+      :unused_options => (f.options.as_flags rescue []),
+      :built_as_bottle => false,
+      :poured_from_bottle => false,
+      :tapped_from => "",
+      :time => nil,
+      :HEAD => nil,
+      :stdlib => nil,
+      :compiler => :clang,
+      :source => {
+        :path => nil,
+      },
+    }
+
+    new(attributes)
   end
 
   def with? val
@@ -139,7 +153,7 @@ class Tab < OpenStruct
   end
 
   def to_json
-    Utils::JSON.dump({
+    attributes = {
       :used_options => used_options.as_flags,
       :unused_options => unused_options.as_flags,
       :built_as_bottle => built_as_bottle,
@@ -148,7 +162,11 @@ class Tab < OpenStruct
       :time => time,
       :HEAD => self.HEAD,
       :stdlib => (stdlib.to_s if stdlib),
-      :compiler => (compiler.to_s if compiler)})
+      :compiler => (compiler.to_s if compiler),
+      :source => source || {},
+    }
+
+    Utils::JSON.dump(attributes)
   end
 
   def write

Library/Homebrew/test/test_tab.rb

@@ -17,6 +17,7 @@ class TabTests < Homebrew::TestCase
       :HEAD               => TEST_SHA1,
       :compiler           => "clang",
       :stdlib             => "libcxx",
+      :source             => { :path => nil },
     })
   end