note about content providers

doc/developer/repoproviders.rst

@@ -38,23 +38,26 @@ It is possible to add new repository providers to BinderHub, allowing
 a BinderHub deployment to fetch repositories from new locations
 on the web. Doing so involves defining your own RepoProvider sub-class
 and modifying a set of methods/attributes to interface with the online
-provider to which you are providing access.
+provider to which you are providing access. It also often involves
+`building a new repo2docker content provider <https://github.com/jupyter/repo2docker/tree/master/repo2docker/contentproviders>`_.
 
 In order to extend the supported repository providers,
 follow these instructions. We'll provide example links for each step to a
 recent `BinderHub pull-request <https://github.com/jupyterhub/binderhub/pull/969>`_
 that implements the ``DataverseProvider`` class.
 
-1. Review the `repoprovider module <https://github.com/jupyterhub/binderhub/blob/master/binderhub/repoproviders.py>`_.
+#. Review the `repoprovider module <https://github.com/jupyterhub/binderhub/blob/master/binderhub/repoproviders.py>`_.
    This shows a number of example repository providers.
-2. Create a new class that sub-classes the ``RepoProvider`` class.
+#. Check whether repo2docker has a `ContentProvider class <https://github.com/jupyter/repo2docker/tree/master/repo2docker/contentproviders>`_
+   that will work with your repository provider. If not, then you'll need to create one first.
+#. Create a new class that sub-classes the ``RepoProvider`` class.
    Define your own methods for actions that are repository provider-specific.
    For example, `here is the DataverseProvider class <https://github.com/jupyterhub/binderhub/pull/969/files#diff-c5688934f1e6dc3e932b6c84c1bbbd5dR298>`_.
-3. Add this class to the `list of default RepoProviders in BinderHub <https://github.com/jupyterhub/binderhub/pull/969/files#diff-a15f2374919ff29de22fa29a192b1fd1R397>`_.
-4. Add the new provider prefix `to the BinderHub UI <https://github.com/jupyterhub/binderhub/pull/969/files#diff-29b962b0b049b65a0fed0d8b5dc838b9R58>`_
+#. Add this class to the `list of default RepoProviders in BinderHub <https://github.com/jupyterhub/binderhub/pull/969/files#diff-a15f2374919ff29de22fa29a192b1fd1R397>`_.
+#. Add the new provider prefix `to the BinderHub UI <https://github.com/jupyterhub/binderhub/pull/969/files#diff-29b962b0b049b65a0fed0d8b5dc838b9R58>`_
    and `the index javascript <https://github.com/jupyterhub/binderhub/pull/969/files#diff-d46aa1f6b1ea4f726708fcc1cd34e994R92>`_
    and make the appropriate changes to the index page based on the URL
    specification for this repository provider.
-5. Add `a test for your repoprovider <https://github.com/jupyterhub/binderhub/pull/969/files#diff-360740f27b99f96e330327e34440a0e8R102>`_
+#. Add `a test for your repoprovider <https://github.com/jupyterhub/binderhub/pull/969/files#diff-360740f27b99f96e330327e34440a0e8R102>`_
    to ensure that it properly resolves and fetches a repository URL.
-6. Document your new repository provider on the :ref:`providers-section` page.
+#. Document your new repository provider on the :ref:`providers-section` page.