Don't add a trailing slash in group redirects

Because we ignored the format, a request to `/groups/foo/labels.json` would
redirect to `/groups/foo/-/labels/.json`. But really, it's worse than that,
because unless the request contained a trailing slash, we shouldn't add one.

Now, we only _keep_ a trailing slash, but don't _add_ one.

lib/gitlab/routing.rb

@@ -46,10 +46,10 @@ module Gitlab
         # Only replace the last occurence of `path`.
         #
         # `request.fullpath` includes the querystring
-        path = request.path.sub(%r{/#{path}/*(?!.*#{path})}, "/-/#{path}/")
-        path << "?#{request.query_string}" if request.query_string.present?
+        new_path = request.path.sub(%r{/#{path}(/*)(?!.*#{path})}, "/-/#{path}\\1")
+        new_path << "?#{request.query_string}" if request.query_string.present?
 
-        path
+        new_path
       end
 
       paths.each do |path|

spec/routing/group_routing_spec.rb

@@ -39,13 +39,19 @@ describe "Groups", "routing" do
 
   describe 'legacy redirection' do
     describe 'labels' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/labels", "/groups/complex.group-namegit/-/labels/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/labels", "/groups/complex.group-namegit/-/labels" do
         let(:resource) { create(:group, parent: group, path: 'labels') }
       end
+
+      context 'when requesting JSON' do
+        it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/labels.json", "/groups/complex.group-namegit/-/labels.json" do
+          let(:resource) { create(:group, parent: group, path: 'labels') }
+        end
+      end
     end
 
     describe 'group_members' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/group_members", "/groups/complex.group-namegit/-/group_members/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/group_members", "/groups/complex.group-namegit/-/group_members" do
         let(:resource) { create(:group, parent: group, path: 'group_members') }
       end
     end
@@ -60,7 +66,7 @@ describe "Groups", "routing" do
     end
 
     describe 'milestones' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones", "/groups/complex.group-namegit/-/milestones/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones", "/groups/complex.group-namegit/-/milestones" do
         let(:resource) { create(:group, parent: group, path: 'milestones') }
       end
 
@@ -76,18 +82,18 @@ describe "Groups", "routing" do
       end
 
       context 'with a query string' do
-        it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones?hello=world", "/groups/complex.group-namegit/-/milestones/?hello=world" do
+        it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones?hello=world", "/groups/complex.group-namegit/-/milestones?hello=world" do
           let(:resource) { create(:group, parent: group, path: 'milestones') }
         end
 
-        it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones?milestones=/milestones", "/groups/complex.group-namegit/-/milestones/?milestones=/milestones" do
+        it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/milestones?milestones=/milestones", "/groups/complex.group-namegit/-/milestones?milestones=/milestones" do
           let(:resource) { create(:group, parent: group, path: 'milestones') }
         end
       end
     end
 
     describe 'edit' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/edit", "/groups/complex.group-namegit/-/edit/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/edit", "/groups/complex.group-namegit/-/edit" do
         let(:resource) do
           pending('still rejected because of the wildcard reserved word')
           create(:group, parent: group, path: 'edit')
@@ -96,29 +102,29 @@ describe "Groups", "routing" do
     end
 
     describe 'issues' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/issues", "/groups/complex.group-namegit/-/issues/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/issues", "/groups/complex.group-namegit/-/issues" do
         let(:resource) { create(:group, parent: group, path: 'issues') }
       end
     end
 
     describe 'merge_requests' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/merge_requests", "/groups/complex.group-namegit/-/merge_requests/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/merge_requests", "/groups/complex.group-namegit/-/merge_requests" do
         let(:resource) { create(:group, parent: group, path: 'merge_requests') }
       end
     end
 
     describe 'projects' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/projects", "/groups/complex.group-namegit/-/projects/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/projects", "/groups/complex.group-namegit/-/projects" do
         let(:resource) { create(:group, parent: group, path: 'projects') }
       end
     end
 
     describe 'activity' do
-      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/activity", "/groups/complex.group-namegit/-/activity/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/complex.group-namegit/activity", "/groups/complex.group-namegit/-/activity" do
         let(:resource) { create(:group, parent: group, path: 'activity') }
       end
 
-      it_behaves_like 'redirecting a legacy path', "/groups/activity/activity", "/groups/activity/-/activity/" do
+      it_behaves_like 'redirecting a legacy path', "/groups/activity/activity", "/groups/activity/-/activity" do
         let!(:parent) { create(:group, path: 'activity') }
         let(:resource) { create(:group, parent: parent, path: 'activity') }
       end