Derive Gist base URL from GitHub url instead of introducing a new environment variable.

Author: ivan-gomes

nbviewer/providers/gist/handlers.py

@@ -18,6 +18,7 @@
     clean_filename,
     quote,
     response_text,
+    url_path_join,
 )
 
 from ..github.handlers import GithubClientMixin
@@ -97,8 +98,11 @@ def get(self, user, **namespace):
                     notebooks=notebooks,
                     description=gist['description'] or '',
                 ))
-        gist_url = os.environ.get('GIST_URL', 'https://gist.github.com/')
-        provider_url = gist_url + u"{user}".format(user=user)
+        if self.github_url == 'https://github.com/':
+            gist_base_url = 'https://gist.github.com/'
+        else:
+            gist_base_url = url_path_join(self.github_url, 'gist/')
+        provider_url = url_path_join(gist_base_url, u"{user}".format(user=user))
         html = self.render_usergists_template(entries=entries, user=user, provider_url=provider_url, 
                                               prev_url=prev_url, next_url=next_url, **namespace
 
@@ -158,12 +162,15 @@ def tree_get(self, user, gist_id, gist, files):
                 e['class'] = 'fa-book'
                 ipynbs.append(e)
             else:
-                gist_url = os.environ.get('GIST_URL', 'https://gist.github.com/')
-                provider_url = gist_url + u"{user}/{gist_id}#file-{clean_name}".format(
+                if self.github_url == 'https://github.com/':
+                    gist_base_url = 'https://gist.github.com/'
+                else:
+                    gist_base_url = url_path_join(self.github_url, 'gist/')
+                provider_url = url_path_join(gist_base_url, u"{user}/{gist_id}#file-{clean_name}".format(
                     user=user,
                     gist_id=gist_id,
                     clean_name=clean_filename(file['filename']),
-                )
+                ))
                 e['url'] = provider_url
                 e['class'] = 'fa-share'
                 others.append(e)
@@ -316,11 +323,11 @@ def uri_rewrites(rewrites=[]):
             u'/{1}'),
     ] 
     # github enterprise
-    if os.environ.get('GIST_URL', '') != '':
-        gist_url = os.environ.get('GIST_URL')
+    if os.environ.get('GITHUB_API_URL', '') != '':
+        gist_base_url = url_path_join(os.environ.get('GITHUB_API_URL').split('/api/v3')[0], 'gist/')
         gist_rewrites.extend([
-            # embedded in URL
-            (r'^' + gist_url + r'([^\/]+/)?([a-f0-9]+)/?$',
+            # Fetching the Gist ID which is embedded in the URL, but with a different base URL
+            (r'^' + gist_base_url + r'([^\/]+/)?([a-f0-9]+)/?$',
                 u'/{1}'),
         ])