Merge branch 'fix-slashes-in-wiki-urls' into 'master'

Fix bug where Wiki pages that include a '/' were no longer accessible

### What does this MR do?

This MR fixes a regression that caused Wiki pages that included a '/' to no longer be accessible.

### Are there points in the code the reviewer needs to double check?

Are there cases that `wiki_helper.rb` doesn't handle?

### Why was this MR needed?

The upgrade from Rails v4.1.2 to v4.1.9 (76aad9b76ed) caused slashes in a model ID to be escaped automatically. We can no longer use the built-in the URL helpers to generate the links for Wiki pages if we want to maintain support for slashes. There is no option to tell the formatter otherwise:

http://stackoverflow.com/questions/25031791/rails-4-1-2-to-param-escapes-slashes-and-breaks-app

The Rails code in question is here:

https://github.com/rails/rails/blob/4-1-stable/actionpack/lib/action_dispatch/journey/visitors.rb#L159

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

#1363

See merge request !502

2 files changed, 27 insertions, 1 deletions

diff --git a/app/controllers/projects/wikis_controller.rb b/app/controllers/projects/wikis_controller.rb
index 643167947b9..aeb7f0699f5 100644
--- a/app/controllers/projects/wikis_controller.rb
+++ b/app/controllers/projects/wikis_controller.rb
@@ -5,6 +5,7 @@ class Projects::WikisController < Projects::ApplicationController
   before_filter :authorize_write_wiki!, only: [:edit, :create, :history]
   before_filter :authorize_admin_wiki!, only: :destroy
   before_filter :load_project_wiki
+  include WikiHelper
 
   def pages
     @wiki_pages = Kaminari.paginate_array(@project_wiki.pages).page(params[:page]).per(PER_PAGE)
@@ -45,7 +46,10 @@ class Projects::WikisController < Projects::ApplicationController
     return render('empty') unless can?(current_user, :write_wiki, @project)
 
     if @page.update(content, format, message)
-      redirect_to [@project.namespace.becomes(Namespace), @project, @page], notice: 'Wiki was successfully updated.'
+      redirect_to(
+        namespace_project_wiki_path(@project.namespace, @project, @page),
+        notice: 'Wiki was successfully updated.'
+      )
     else
       render 'edit'
     end
diff --git a/app/helpers/wiki_helper.rb b/app/helpers/wiki_helper.rb
new file mode 100644
index 00000000000..a3bc64c010e
--- /dev/null
+++ b/app/helpers/wiki_helper.rb
@@ -0,0 +1,22 @@
+module WikiHelper
+  # Rails v4.1.9+ escapes all model IDs, converting slashes into %2F. The
+  # only way around this is to implement our own path generators.
+  def namespace_project_wiki_path(namespace, project, wiki_page, *args)
+    slug =
+        case wiki_page
+        when Symbol
+          wiki_page
+        else
+          wiki_page.slug
+        end
+    namespace_project_path(namespace, project) + "/wikis/#{slug}"
+  end
+
+  def edit_namespace_project_wiki_path(namespace, project, wiki_page, *args)
+    namespace_project_wiki_path(namespace, project, wiki_page) + '/edit'
+  end
+
+  def history_namespace_project_wiki_path(namespace, project, wiki_page, *args)
+    namespace_project_wiki_path(namespace, project, wiki_page) + '/history'
+  end
+end