Prevent rewritting plain links as embedded

Prevents rewritting plain image/video links as embedded when moving
issues.

changelogs/unreleased/issue_58494.yml

+---
+title: Prevent turning plain links into embedded when moving issues
+merge_request: 31489
+author:
+type: fixed

lib/gitlab/gfm/uploads_rewriter.rb

@@ -27,7 +27,15 @@ module Gitlab
 
           klass = target_parent.is_a?(Namespace) ? NamespaceFileUploader : FileUploader
           moved = klass.copy_to(file, target_parent)
-          moved.markdown_link
+
+          moved_markdown = moved.markdown_link
+
+          # Prevents rewrite of plain links as embedded
+          if was_embedded?(markdown)
+            moved_markdown
+          else
+            moved_markdown.sub(/\A!/, "")
+          end
         end
       end
 
@@ -43,6 +51,10 @@ module Gitlab
         referenced_files.compact.select(&:exists?)
       end
 
+      def was_embedded?(markdown)
+        markdown.starts_with?("!")
+      end
+
       private
 
       def find_file(project, secret, file)

spec/lib/gitlab/gfm/uploads_rewriter_spec.rb

@@ -55,6 +55,17 @@ describe Gitlab::Gfm::UploadsRewriter do
       end
     end
 
+    it 'does not rewrite plain links as embedded' do
+      embedded_link = image_uploader.markdown_link
+      plain_image_link = embedded_link.sub(/\A!/, "")
+      text = "#{plain_image_link} and #{embedded_link}"
+
+      moved_text = described_class.new(text, old_project, user).rewrite(new_project)
+
+      expect(moved_text.scan(/!\[.*?\]/).count).to eq(1)
+      expect(moved_text.scan(/\A\[.*?\]/).count).to eq(1)
+    end
+
     context "file are stored locally" do
       include_examples "files are accessible"
     end