Fix API project lookups when querying with a namespace with dots

Attempting to use the /projects/:id API by specifying :id in
"namespace/project" format would always result in a 404 if the namespace
contained a dot.

The reason? From http://guides.rubyonrails.org/routing.html#specifying-constraints:

"By default the :id parameter doesn't accept dots - this is because the dot is
used as a separator for formatted routes. If you need to use a dot within an
:id add a constraint which overrides this - for example id: /[^\/]+/ allows
anything except a slash."

Closes https://github.com/gitlabhq/gitlabhq/issues/9573

CHANGELOG

@@ -13,6 +13,7 @@ v 8.4.0 (unreleased)
   - Revert back upvote and downvote button to the issue and MR pages
   - Swap position of Assignee and Author selector on Issuables (Zeger-Jan van de Weg)
   - Fix version check image in Safari
+  - Fix API project lookups when querying with a namespace with dots (Stan Hu)
 
 v 8.3.3 (unreleased)
   - Fix project transfer e-mail sending incorrect paths in e-mail notification (Stan Hu)

lib/api/projects.rb

@@ -3,7 +3,7 @@ module API
   class Projects < Grape::API
     before { authenticate! }
 
-    resource :projects do
+    resource :projects, requirements: { id: /[^\/]+/ } do
       helpers do
         def map_public_to_visibility_level(attrs)
           publik = attrs.delete(:public)

spec/requests/api/projects_spec.rb

@@ -382,6 +382,15 @@ describe API::API, api: true  do
       expect(response.status).to eq(404)
     end
 
+    it 'should handle users with dots' do
+      dot_user = create(:user, username: 'dot.user')
+      project = create(:project, creator_id: dot_user.id, namespace: dot_user.namespace)
+
+      get api("/projects/#{dot_user.namespace.name}%2F#{project.path}", dot_user)
+      expect(response.status).to eq(200)
+      expect(json_response['name']).to eq(project.name)
+    end
+
     describe 'permissions' do
       context 'all projects' do
         it 'Contains permission information' do