Merge pull request #1913 from rkdarst/announcement_text

Add customizable announcement text on home,login,logout,spawn

docs/source/reference/templates.md

@@ -59,3 +59,35 @@ text about the server starting up, place this content in a file named
 <p>Patience is a virtue.</p>
 {% endblock %}
 ```
+
+## Page Announcements
+
+To add announcements to be displayed on a page, you have two options:
+
+- Extend the page templates as described above
+- Use configuration variables
+
+### Announcement Configuration Variables
+
+If you set the configuration variable `JupyterHub.template_vars =
+{'announcement': 'some_text}`, the given `some_text` will be placed on
+the top of all pages.  The more specific variables
+`announcement_login`, `announcement_spawn`, `announcement_home`, and
+`announcement_logout` are more specific and only show on their
+respective pages (overriding the global `announcement` variable).
+Note that changing these varables require a restart, unlike direct
+template extension.
+
+You can get the same effect by extending templates, which allows you
+to update the messages without restarting.  Set
+`c.JupyterHub.template_paths` as mentioned above, and then create a
+template (for example, `login.html`) with:
+
+```html
+{% extends "templates/login.html" %}
+{% set announcement = 'some message' %}
+```
+
+Extending `page.html` puts the message on all pages, but note that
+extending `page.html` take precedence over an extension of a specific
+page (unlike the variable-based approach above).