1 files changed, 5 insertions, 1 deletions
diff --git a/Library/Homebrew/cmd/update.rb b/Library/Homebrew/cmd/update.rb
index 5addb4375..85cc3014b 100644
--- a/Library/Homebrew/cmd/update.rb
+++ b/Library/Homebrew/cmd/update.rb
@@ -172,7 +172,7 @@ class Updater
     map = Hash.new{ |h,k| h[k] = [] }
 
     if initial_revision && initial_revision != current_revision
-      `git diff-tree -r --name-status --diff-filter=AMD #{initial_revision} #{current_revision}`.each_line do |line|
+      diff.each_line do |line|
         status, path = line.split
         map[status.to_sym] << repository.join(path)
       end
@@ -187,6 +187,10 @@ class Updater
     `git rev-parse -q --verify HEAD`.chomp
   end
 
+  def diff
+    `git diff-tree -r --name-status --diff-filter=AMD #{initial_revision} #{current_revision}`
+  end
+
   def `(cmd)
     out = super
     if $? && !$?.success?