Merge pull request #2852 from mdeniz/make_evans_migration_reversible

Make Evan's migration about cache line key length reversible

src/api/db/migrate/20170317094221_change_cache_lines_key.rb

@@ -1,5 +1,9 @@
 class ChangeCacheLinesKey < ActiveRecord::Migration[5.0]
-  def change
+  def up
     change_column(:cache_lines, :key, :string, limit: 4096)
   end
+
+  def down
+    change_column(:cache_lines, :key, :string, limit: 255)
+  end
 end