Add documentation for wildcard protected branches.

app/views/projects/protected_branches/index.html.haml

@@ -23,7 +23,8 @@
           = f.label :name, "Branch", class: "label-light"
           = f.text_field(:name)
           %p.help-block
-            Wildcards such as
+            = link_to "Wildcards", help_page_path(category: 'workflow', file: 'protected_branches', format: 'md', anchor: "wildcard-protected-branches")
+            such as
             %code *-stable
             or
             %code production/*

doc/workflow/protected_branches.md

-# Protected branches
+# Protected Branches
 
 Permissions in GitLab are fundamentally defined around the idea of having read or write permission to the repository and branches.
 
@@ -28,4 +28,28 @@ For those workflows, you can allow everyone with write access to push to a prote
 
 On already protected branches you can also allow developers to push to the repository by selecting the `Developers can push` check box.
 
-![Developers can push](protected_branches/protected_branches2.png)
\ No newline at end of file
+![Developers can push](protected_branches/protected_branches2.png)
+
+## Wildcard Protected Branches
+
+>**Note:**
+This feature was added in GitLab 8.10.
+
+1. You can specify a wildcard protected branch, which will protect all branches matching the wildcard. For example:
+
+    | Wildcard Protected Branch | Matching Branches                                      |
+    |---------------------------+--------------------------------------------------------|
+    | `*-stable`                | `production-stable`, `staging-stable`                  |
+    | `production/*`            | `production/app-server`, `production/load-balancer`    |
+    | `*gitlab*`                | `gitlab`, `gitlab/staging`, `master/gitlab/production` |
+
+1. Protected branch settings (like "Developers Can Push") apply to all matching branches.
+
+1. Two different wildcards can potentially match the same branch. For example, `*-stable` and `production-*` would both match a `production-stable` branch.
+   >**Note:**
+   If _any_ of these protected branches have "Developers Can Push" set to true, then `production-stable` has it set to true.
+
+1. If you click on a protected branch's name, you will be presented with a list of all matching branches:
+
+    ![protected branch matches](protected_branches/protected_branches3.png)
+