Add merge_commit_sha column to merge_requests.

app/models/merge_request.rb

@@ -24,6 +24,7 @@
 #  merge_params              :text
 #  merge_when_build_succeeds :boolean          default(FALSE), not null
 #  merge_user_id             :integer
+#  merge_commit_sha          :string
 #
 
 require Rails.root.join("app/models/commit")

db/schema.rb

@@ -525,6 +525,7 @@ ActiveRecord::Schema.define(version: 20160209130428) do
     t.text     "merge_params"
     t.boolean  "merge_when_build_succeeds", default: false, null: false
     t.integer  "merge_user_id"
+    t.string   "merge_commit_sha"
   end
 
   add_index "merge_requests", ["assignee_id"], name: "index_merge_requests_on_assignee_id", using: :btree