Fix submodule links to gist.github.com

app/helpers/submodule_helper.rb

@@ -38,6 +38,8 @@ module SubmoduleHelper
          url_helpers.namespace_project_tree_path(namespace, project, submodule_item_id)]
       elsif relative_self_url?(url)
         relative_self_links(url, submodule_item_id, repository.project)
+      elsif gist_github_dot_com_url?(url)
+        gist_github_com_tree_links(namespace, project, submodule_item_id)
       elsif github_dot_com_url?(url)
         github_com_tree_links(namespace, project, submodule_item_id)
       elsif gitlab_dot_com_url?(url)
@@ -52,6 +54,10 @@ module SubmoduleHelper
 
   protected
 
+  def gist_github_dot_com_url?(url)
+    url =~ %r{gist\.github\.com[/:][^/]+/[^/]+\Z}
+  end
+
   def github_dot_com_url?(url)
     url =~ %r{github\.com[/:][^/]+/[^/]+\Z}
   end
@@ -78,6 +84,11 @@ module SubmoduleHelper
     [base, [base, '/-/tree/', commit].join('')]
   end
 
+  def gist_github_com_tree_links(namespace, project, commit)
+    base = ['https://gist.github.com/', namespace, '/', project].join('')
+    [base, [base, commit].join('/')]
+  end
+
   def github_com_tree_links(namespace, project, commit)
     base = ['https://github.com/', namespace, '/', project].join('')
     [base, [base, '/tree/', commit].join('')]

changelogs/unreleased/26111-fix-github-gist-links.yml

+---
+title: Fix submodule links to gist.github.com
+merge_request: 27346
+author:
+type: fixed

spec/helpers/submodule_helper_spec.rb

@@ -81,6 +81,33 @@ describe SubmoduleHelper do
       end
     end
 
+    context 'submodule on gist.github.com' do
+      it 'detects ssh' do
+        stub_url('git@gist.github.com:gitlab-org/gitlab-foss.git')
+        is_expected.to eq(['https://gist.github.com/gitlab-org/gitlab-foss', 'https://gist.github.com/gitlab-org/gitlab-foss/hash'])
+      end
+
+      it 'detects http' do
+        stub_url('http://gist.github.com/gitlab-org/gitlab-foss.git')
+        is_expected.to eq(['https://gist.github.com/gitlab-org/gitlab-foss', 'https://gist.github.com/gitlab-org/gitlab-foss/hash'])
+      end
+
+      it 'detects https' do
+        stub_url('https://gist.github.com/gitlab-org/gitlab-foss.git')
+        is_expected.to eq(['https://gist.github.com/gitlab-org/gitlab-foss', 'https://gist.github.com/gitlab-org/gitlab-foss/hash'])
+      end
+
+      it 'handles urls with no .git on the end' do
+        stub_url('http://gist.github.com/gitlab-org/gitlab-foss')
+        is_expected.to eq(['https://gist.github.com/gitlab-org/gitlab-foss', 'https://gist.github.com/gitlab-org/gitlab-foss/hash'])
+      end
+
+      it 'returns original with non-standard url' do
+        stub_url('http://gist.github.com/another/gitlab-org/gitlab-foss.git')
+        is_expected.to eq([repo.submodule_url_for, nil])
+      end
+    end
+
     context 'submodule on github.com' do
       it 'detects ssh' do
         stub_url('git@github.com:gitlab-org/gitlab-foss.git')