1 files changed, 45 insertions, 0 deletions
diff --git a/lib/gitlab/ci/project_config/external_project.rb b/lib/gitlab/ci/project_config/external_project.rb
new file mode 100644
index 00000000000..0ed5d6fa226
--- /dev/null
+++ b/lib/gitlab/ci/project_config/external_project.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class ProjectConfig
+      class ExternalProject < Source
+        def content
+          strong_memoize(:content) do
+            next unless external_project_path?
+
+            path_file, path_project, ref = extract_location_tokens
+
+            config_location = { 'project' => path_project, 'file' => path_file }
+            config_location['ref'] = ref if ref.present?
+
+            YAML.dump('include' => [config_location])
+          end
+        end
+
+        def source
+          :external_project_source
+        end
+
+        private
+
+        # Example: path/to/.gitlab-ci.yml@another-group/another-project
+        def external_project_path?
+          ci_config_path =~ /\A.+(yml|yaml)@.+\z/
+        end
+
+        # Example: path/to/.gitlab-ci.yml@another-group/another-project:refname
+        def extract_location_tokens
+          path_file, path_project = ci_config_path.split('@', 2)
+
+          if path_project.include? ":"
+            project, ref = path_project.split(':', 2)
+            [path_file, project, ref]
+          else
+            [path_file, path_project]
+          end
+        end
+      end
+    end
+  end
+end