merge migrations to 1 single create per table

also:

* reorder table columns
* no need for `add_concurrent_index`
* no need for explicit index removal on `#down`

db/migrate/20170222111732_create_gpg_keys.rb

@@ -3,11 +3,16 @@ class CreateGpgKeys < ActiveRecord::Migration
 
   def change
     create_table :gpg_keys do |t|
+      t.timestamps_with_timezone null: false
+
+      t.references :user, index: true, foreign_key: true
+
       t.string :fingerprint
+      t.string :primary_keyid
+
       t.text :key
-      t.references :user, index: true, foreign_key: true
 
-      t.timestamps_with_timezone null: false
+      t.index :primary_keyid
     end
   end
 end

db/migrate/20170613103429_add_primary_keyid_to_gpg_keys.rb

-class AddPrimaryKeyidToGpgKeys < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-
-  DOWNTIME = false
-
-  disable_ddl_transaction!
-
-  def up
-    add_column :gpg_keys, :primary_keyid, :string
-    add_concurrent_index :gpg_keys, :primary_keyid
-  end
-
-  def down
-    remove_concurrent_index :gpg_keys, :primary_keyid if index_exists?(:gpg_keys, :primary_keyid)
-    remove_column :gpg_keys, :primary_keyid, :string
-  end
-end

db/migrate/20170613154149_create_gpg_signatures.rb

 class CreateGpgSignatures < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-
   DOWNTIME = false
 
-  disable_ddl_transaction!
-
-  def up
+  def change
     create_table :gpg_signatures do |t|
-      t.string :commit_sha
+      t.timestamps_with_timezone null: false
+
       t.references :project, index: true, foreign_key: true
       t.references :gpg_key, index: true, foreign_key: true
-      t.string :gpg_key_primary_keyid
-      t.boolean :valid_signature
 
-      t.timestamps_with_timezone null: false
-    end
-
-    add_concurrent_index :gpg_signatures, :commit_sha
-    add_concurrent_index :gpg_signatures, :gpg_key_primary_keyid
-  end
+      t.boolean :valid_signature
 
-  def down
-    remove_concurrent_index :gpg_signatures, :commit_sha if index_exists?(:gpg_signatures, :commit_sha)
-    remove_concurrent_index :gpg_signatures, :gpg_key_primary_keyid if index_exists?(:gpg_signatures, :gpg_key_primary_keyid)
+      t.string :commit_sha
+      t.string :gpg_key_primary_keyid
+      t.string :gpg_key_user_name
+      t.string :gpg_key_user_email
 
-    drop_table :gpg_signatures
+      t.index :commit_sha
+      t.index :gpg_key_primary_keyid
+    end
   end
 end

db/migrate/20170713104235_add_gpg_key_user_info_to_gpg_signatures.rb

-# See http://doc.gitlab.com/ce/development/migration_style_guide.html
-# for more information on how to write migrations for GitLab.
-
-class AddGpgKeyUserInfoToGpgSignatures < ActiveRecord::Migration
-  DOWNTIME = false
-
-  def change
-    add_column :gpg_signatures, :gpg_key_user_name, :string
-    add_column :gpg_signatures, :gpg_key_user_email, :string
-  end
-end

db/schema.rb

@@ -541,25 +541,25 @@ ActiveRecord::Schema.define(version: 20170725145659) do
   add_index "forked_project_links", ["forked_to_project_id"], name: "index_forked_project_links_on_forked_to_project_id", unique: true, using: :btree
 
   create_table "gpg_keys", force: :cascade do |t|
-    t.string "fingerprint"
-    t.text "key"
-    t.integer "user_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.integer "user_id"
+    t.string "fingerprint"
     t.string "primary_keyid"
+    t.text "key"
   end
 
   add_index "gpg_keys", ["primary_keyid"], name: "index_gpg_keys_on_primary_keyid", using: :btree
   add_index "gpg_keys", ["user_id"], name: "index_gpg_keys_on_user_id", using: :btree
 
   create_table "gpg_signatures", force: :cascade do |t|
-    t.string "commit_sha"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
     t.integer "project_id"
     t.integer "gpg_key_id"
-    t.string "gpg_key_primary_keyid"
     t.boolean "valid_signature"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.string "commit_sha"
+    t.string "gpg_key_primary_keyid"
     t.string "gpg_key_user_name"
     t.string "gpg_key_user_email"
   end