Add Timelog model to persist spent time on Issues/MergeRequests.

app/models/concerns/issuable.rb

@@ -37,6 +37,7 @@ module Issuable
     has_many :label_links, as: :target, dependent: :destroy
     has_many :labels, through: :label_links
     has_many :todos, as: :target, dependent: :destroy
+    has_many :timelogs, as: :trackable, dependent: :destroy
 
     has_one :metrics
 

app/models/timelog.rb

+class Timelog < ActiveRecord::Base
+  belongs_to :trackable, polymorphic: true
+end

db/migrate/20161030020610_create_timelogs.rb

+class CreateTimelogs < ActiveRecord::Migration
+  def change
+    create_table :timelogs do |t|
+      t.integer :time_spent, null: false
+      t.references :trackable, polymorphic: true
+
+      t.timestamps null: false
+    end
+
+    add_index :timelogs, [:trackable_type, :trackable_id]
+  end
+end

db/schema.rb

@@ -1253,6 +1253,16 @@ ActiveRecord::Schema.define(version: 20161106185620) do
 
   add_index "tags", ["name"], name: "index_tags_on_name", unique: true, using: :btree
 
+  create_table "timelogs", force: :cascade do |t|
+    t.integer "time_spent", null: false
+    t.integer "trackable_id"
+    t.string "trackable_type"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
+  add_index "timelogs", ["trackable_type", "trackable_id"], name: "index_timelogs_on_trackable_type_and_trackable_id", using: :btree
+
   create_table "todos", force: :cascade do |t|
     t.integer "user_id", null: false
     t.integer "project_id", null: false