Merge branch 'db-copy-as-gfm-prosemirror-ee' into 'master'

[EE]  Reimplement Copy-as-GFM using the prosemirror document model

See merge request gitlab-org/gitlab-ee!9288

lib/banzai/pipeline/gfm_pipeline.rb

@@ -5,11 +5,11 @@ module Banzai
     class GfmPipeline < BasePipeline
       prepend EE::Banzai::Pipeline::GfmPipeline # rubocop: disable Cop/InjectEnterpriseEditionModule
 
-      # These filters convert GitLab Flavored Markdown (GFM) to HTML.
-      # The handlers defined in app/assets/javascripts/behaviors/markdown/copy_as_gfm.js
-      # consequently convert that same HTML to GFM to be copied to the clipboard.
-      # Every filter that generates HTML from GFM should have a handler in
-      # app/assets/javascripts/behaviors/markdown/copy_as_gfm.js, in reverse order.
+      # These filters transform GitLab Flavored Markdown (GFM) to HTML.
+      # The nodes and marks referenced in app/assets/javascripts/behaviors/markdown/editor_extensions.js
+      # consequently transform that same HTML to GFM to be copied to the clipboard.
+      # Every filter that generates HTML from GFM should have a node or mark in
+      # app/assets/javascripts/behaviors/markdown/editor_extensions.js.
       # The GFM-to-HTML-to-GFM cycle is tested in spec/features/copy_as_gfm_spec.rb.
       def self.filters
         @filters ||= FilterArray[