fix: allow absolute paths for notebooks

voila/app.py

@@ -33,6 +33,7 @@
 from jupyter_server.services.config import ConfigManager
 from jupyter_server.base.handlers import FileFindHandler
 from jupyter_core.paths import jupyter_config_path, jupyter_path
+from ipython_genutils.py3compat import getcwd
 
 from .paths import ROOT, STATIC_ROOT, collect_template_paths
 from .handler import VoilaHandler
@@ -71,6 +72,9 @@ class VoilaBase(Application):
         config=True,
         help='Will autoreload to server and the page when a template, js file or Python code changes'
     )
+    root_dir = Unicode(config=True,
+        help="The directory to use for notebooks."
+    )
     static_root = Unicode(
         STATIC_ROOT,
         config=True,
@@ -126,6 +130,13 @@ def nbextensions_path(self):
             path.append(os.path.join(get_ipython_dir(), 'nbextensions'))
         return path
 
+    @default('root_dir')
+    def _default_root_dir(self):
+        if self.notebook_path:
+            return os.path.dirname(os.path.abspath(self.notebook_path))
+        else:
+            return getcwd()
+
     def parse_command_line(self, argv=None):
         super(VoilaBase, self).parse_command_line(argv)
         self.notebook_path = self.extra_args[0] if len(self.extra_args) == 1 else None
@@ -167,7 +178,7 @@ def start(self):
         env = jinja2.Environment(loader=jinja2.FileSystemLoader(self.template_paths), extensions=['jinja2.ext.i18n'], **jenv_opt)
         nbui = gettext.translation('nbui', localedir=os.path.join(ROOT, 'i18n'), fallback=True)
         env.install_gettext_translations(nbui, newstyle=False)
-        contents_manager = LargeFileManager()  # TODO: make this configurable like notebook
+        contents_manager = LargeFileManager(parent=self)  # TODO: make this configurable like notebook
 
         # we create a config manager that load both the serverconfig and nbconfig (classical notebook)
         read_config_path = [os.path.join(p, 'serverconfig') for p in jupyter_config_path()]
@@ -220,7 +231,7 @@ def start(self):
                 url_path_join(base_url, r'/'),
                 VoilaHandler,
                 {
-                    'notebook_path': self.notebook_path,
+                    'notebook_path': os.path.relpath(self.notebook_path, self.root_dir),
                     'strip_sources': self.strip_sources,
                     'nbconvert_template_paths': self.nbconvert_template_paths,
                     'config': self.config