Env variables for server root & URL in terminals

This came up on reddit: if you want to open a notebook or a file in the
text editor from the terminal inside the notebook web interface, you can
construct a URL to open. But to do that accurately, you need to know the
root directory where the server is looking, and the first part of the
URL. This exposes both of those as environment variables:
$JUPYTER_SERVER_ROOT and $JUPYTER_SERVER_URL.

notebook/notebookapp.py

@@ -889,7 +889,7 @@ class NotebookApp(JupyterApp):
     def init_terminals(self):
         try:
             from .terminal import initialize
-            initialize(self.web_app)
+            initialize(self.web_app, self.notebook_dir, self.connection_url)
             self.web_app.settings['terminals_available'] = True
         except ImportError as e:
             log = self.log.debug if sys.platform == 'win32' else self.log.warn

notebook/terminal/__init__.py

@@ -12,9 +12,14 @@ from notebook.utils import url_path_join as ujoin
 from .handlers import TerminalHandler, TermSocket
 from . import api_handlers
 
-def initialize(webapp):
+def initialize(webapp, notebook_dir, connection_url):
     shell = os.environ.get('SHELL') or 'sh'
-    terminal_manager = webapp.settings['terminal_manager'] = NamedTermManager(shell_command=[shell])
+    terminal_manager = webapp.settings['terminal_manager'] = NamedTermManager(
+        shell_command=[shell],
+        extra_env={'JUPYTER_SERVER_ROOT': notebook_dir,
+                   'JUPYTER_SERVER_URL': connection_url,
+                   },
+    )
     terminal_manager.log = app_log
     base_url = webapp.settings['base_url']
     handlers = [
@@ -24,4 +29,4 @@ def initialize(webapp):
         (ujoin(base_url, r"/api/terminals"), api_handlers.TerminalRootHandler),
         (ujoin(base_url, r"/api/terminals/(\w+)"), api_handlers.TerminalHandler),
     ]
-    webapp.add_handlers(".*$", handlers)
+    webapp.add_handlers(".*$", handlers)