fixed merge request diff

app/controllers/merge_requests_controller.rb

@@ -34,8 +34,9 @@ def commits
   end
 
   def diffs
-    @commit = @project.commit(@merge_request.source_branch)
-    @diffs = @project.repo.diff(@merge_request.target_branch, @merge_request.source_branch)
+    @diffs = @merge_request.diffs
+    @commit = @merge_request.last_commit
+
     render :template => "merge_requests/_diffs", :layout => false
   end
 

app/models/commit.rb

@@ -36,4 +36,8 @@ def author_email
   def author_name
     encode(author.name)
   end
+
+  def prev_commit
+    parents.first
+  end
 end

app/models/merge_request.rb

@@ -33,4 +33,14 @@ class MergeRequest < ActiveRecord::Base
   def new?
     today? && created_at == updated_at
   end
+
+  def diffs
+    commit = project.commit(source_branch)
+    commits = project.repo.commits_between(target_branch, source_branch).map {|c| Commit.new(c)}
+    diffs = project.repo.diff(commits.first.prev_commit.id, commits.last.id)
+  end
+
+  def last_commit
+    project.commit(source_branch)
+  end
 end