Record HEAD SHA and date of installs in receipt

Library/Homebrew/extend/string.rb

@@ -21,6 +21,17 @@ class String
       self[0, prefix.length] == prefix
     end
   end
+
+  # String.chomp, but if result is empty: returns nil instead.
+  # Allows `chuzzle || foo` short-circuits.
+  def chuzzle
+    s = chomp
+    s unless s.empty?
+  end
+end
+
+class NilClass
+  def chuzzle; end
 end
 
 # used by the inreplace function (in utils.rb)

Library/Homebrew/tab.rb

@@ -9,17 +9,19 @@ require 'vendor/multi_json'
 # `Tab.for_install`.
 class Tab < OpenStruct
   def self.for_install f, args
+    sha = `cd '#{HOMEBREW_REPOSITORY}' && git rev-parse --verify -q HEAD 2>/dev/null`.chuzzle
     Tab.new :used_options => args.used_options(f),
             :unused_options => args.unused_options(f),
             :tabfile => f.prefix + "INSTALL_RECEIPT.json",
             :built_as_bottle => !!args.build_bottle?,
-            :tapped_from => f.tap
+            :tapped_from => f.tap,
+            :time => Time.now.to_i, # to_s would be better but Ruby has no from_s function :P
+            :HEAD => sha
   end
 
   def self.from_file path
     tab = Tab.new MultiJson.decode(open(path).read)
     tab.tabfile = path
-
     return tab
   end
 
@@ -35,7 +37,9 @@ class Tab < OpenStruct
         Tab.new :used_options => [],
                 :unused_options => [],
                 :built_as_bottle => false,
-                :tapped_from => ""
+                :tapped_from => "",
+                :time => nil,
+                :HEAD => nil
       end
     end
   end
@@ -63,7 +67,9 @@ class Tab < OpenStruct
     Tab.new :used_options => [],
             :unused_options => f.build.as_flags,
             :built_as_bottle => false,
-            :tapped_from => ""
+            :tapped_from => "",
+            :time => nil,
+            :HEAD => nil
   end
 
   def installed_with? opt
@@ -79,8 +85,9 @@ class Tab < OpenStruct
       :used_options => used_options,
       :unused_options => unused_options,
       :built_as_bottle => built_as_bottle,
-      :tapped_from => tapped_from
-    })
+      :tapped_from => tapped_from,
+      :time => time,
+      :HEAD => send("HEAD")})
   end
 
   def write