Add missing doc file

docs/gl_objects/protected_branches.rst

@@ -0,0 +1,44 @@
+##################
+Protected branches
+##################
+
+You can define a list of protected branch names on a repository. Names can use
+wildcards (``*``).
+
+References
+----------
+
+* v4 API:
+
+  + :class:`gitlab.v4.objects.ProjectProtectedBranch`
+  + :class:`gitlab.v4.objects.ProjectProtectedBranchManager`
+  + :attr:`gitlab.v4.objects.Project.protectedbranches`
+
+* GitLab API: https://docs.gitlab.com/ce/api/protected_branches.html#protected-branches-api
+
+Examples
+--------
+
+Get the list of protected branches for a project:
+
+.. literalinclude:: branches.py
+   :start-after: # p_branch list
+   :end-before: # end p_branch list
+
+Get a single protected branch:
+
+.. literalinclude:: branches.py
+   :start-after: # p_branch get
+   :end-before: # end p_branch get
+
+Create a protected branch:
+
+.. literalinclude:: branches.py
+   :start-after: # p_branch create
+   :end-before: # end p_branch create
+
+Delete a protected branch:
+
+.. literalinclude:: branches.py
+   :start-after: # p_branch delete
+   :end-before: # end p_branch delete