docs: reference nbgitpullers docs to fix outdated tljh docs

docs/howto/content/nbgitpuller.rst

@@ -24,7 +24,7 @@ Instructors should be able to:
 1. Use modern collaborative version control tools to author & store their
    materials. This currently means using Git.
 
-**nbgitpuller** is a Jupyter Notebook extension that helps achieve these goals.
+**nbgitpuller** is a Jupyter server extension that helps achieve these goals.
 This tutorial will walk you through the process of creating a magic
 nbgitpuller link that users of your JupyterHub can click to fetch the latest
 version of materials from a git repo.
@@ -38,76 +38,10 @@ Pre-requisites
 Step 1: Generate nbgitpuller link
 =================================
 
-**Generate the link with a Binder app**.
-
-#. The easiest way to generate an nbgitpuller link is to use the
-   `mybinder.org based application <https://github.com/jupyterhub/nbgitpuller>`_.
-   Open it, and wait for it to load.
-
-   .. image:: ../../images/nbgitpuller/binder-progress.png
-      :alt: Progress bar as the binder application loads
-
-#. A blank form with some help text will open up.
-
-   .. image:: ../../images/nbgitpuller/blank-application.png
-      :alt: Blank application to make nbgitpuller links
-
-#. Enter the IP address or URL to your JupyterHub under ``hub_url``.
-   Include ``http://`` or ``https://`` as appropriate.
-
-   .. image:: ../../images/nbgitpuller/hub-url-application.png
-      :alt: Application with hub_url filled out
-
-#. Enter the URL to your Git repository. This could be from GitHub,
-   GitLab or any other git provider - including the disk of the
-   server The Littlest JupyterHub is installed on. As you start
-   typing the URL here, you'll notice that the link is already
-   being printed below!
-
-   .. image:: ../../images/nbgitpuller/git-url-application.png
-      :alt: Application with git_url filled out
-
-#. If your git repository is using a non-default branch name,
-   you can specify that under ``branch``. Most people do not
-   need to customize this.
-
-#. If you want to open a specific notebook when the user clicks
-   on the link, specify the path to the notebook under ``filepath``.
-   Make sure this file exists, otherwise users will get a 'File not found'
-   error.
-
-   .. image:: ../../images/nbgitpuller/filepath-application.png
-      :alt: Application with filepath filled out
-
-   If you do not specify a file path, the user will be shown the
-   directory listing for the repository.
-
-#. By default, notebooks will be opened in the classic Jupyter Notebook
-   interface. You can select ``lab`` under ``application`` to open it in the
-   `JupyterLab <https://github.com/jupyterlab/jupyterlab>`_ instead.
-
-The link printed at the bottom of the form can be distributed to students
-now! You can also click it to test that it is working as intended,
-and adjust the form values until you get something you are happy with.
-
-**Hand-craft your nbgitpuller link**
-
-If you'd prefer to hand-craft your ``nbgitpuller`` link (e.g. if the Binder
-link above doesn't work), you can use the following pattern::
-
-   http://<my-jhub-address>/hub/user-redirect/git-pull?repo=<your-repo-url>&branch=<your-branch-name>&subPath=<subPath>&app=<notebook | lab>
-
-- **repo** is the URL of the git repository you want to clone. This parameter is required.
-- **branch** is the branch name to use when cloning from the repository.
-  This parameter is optional and defaults to ``master``.
-- **subPath** is the path of the directory / notebook inside the repo to launch after cloning.
-  This parameter is optional, and defaults to opening the base directory of the linked Git repository.
-- **app** This parameter is optional and defaults to either the environment variable
-  `NBGITPULLER_APP`'s value or `notebook` if it is undefined. The allowed values
-  are `lab` and `notebook`, the value will determine in what application view
-  you end up in.
-- **urlPath** will, if specified, override `app` and `subPath` and redirect
-  blindly to the specified path.
+The quickest way to generate a link is to use `nbgitpuller.link
+<https://nbgitpuller.link>`_, but other options exist as described in the
+`nbgitpuller project's documentation
+<https://jupyterhub.github.io/nbgitpuller/use.html>`_.
 
 Step 2: Users click on the nbgitpuller link
 ===========================================
@@ -130,9 +64,3 @@ Step 2: Users click on the nbgitpuller link
 
 This workflow lets users land directly in the notebook you specified
 without having to understand much about git or the JupyterHub interface.
-
-Advanced: hand-crafting an nbgitpuller link
-===========================================
-
-For information on hand-crafting an ``nbgitpuller`` link, see
-`the nbgitpuller README <https://github.com/jupyterhub/nbgitpuller#constructing-the-nbgitpuller-url>`_.