Add custom OmniAuth strategy for Bitbucket OAuth2

config/initializers/omniauth.rb

@@ -26,3 +26,9 @@ if Gitlab.config.omniauth.enabled
     end
   end
 end
+
+module OmniAuth
+  module Strategies
+    autoload :Bitbucket, Rails.root.join('lib', 'omniauth', 'strategies', 'bitbucket')
+  end
+end

lib/omniauth/strategies/bitbucket.rb

+require 'omniauth-oauth2'
+
+module OmniAuth
+  module Strategies
+    class Bitbucket < OmniAuth::Strategies::OAuth2
+      option :name, 'bitbucket'
+
+      option :client_options, {
+        site: 'https://bitbucket.org',
+        authorize_url: 'https://bitbucket.org/site/oauth2/authorize',
+        token_url: 'https://bitbucket.org/site/oauth2/access_token'
+      }
+
+      def callback_url
+        full_host + script_name + callback_path
+      end
+
+      uid do
+        raw['username']
+      end
+
+      info do
+        {
+          name: raw_info['display_name'],
+          avatar: raw_info['links']['avatar']['href'],
+          email: primary_email
+        }
+      end
+
+      def raw_info
+        @raw_info ||= access_token.get('user').parsed
+      end
+
+      def primary_email
+        primary = emails.find{ |i| i['is_primary'] && i['is_confirmed'] }
+        primary && primary['email'] || nil
+      end
+
+      def emails
+        email_response = access_token.get('user/emails').parsed
+        @emails ||= email_response && email_response['values'] || nil
+      end
+    end
+  end
+end