add 'globals' instead of overwriting the default (#3773)

docs/configuration.rst

@@ -4740,15 +4740,13 @@ Type
 Example
     * ``"~/.local/share/gdl-globals.py"``
     * ``"gdl-globals"``
-Default
-    The ``GLOBALS`` dict in
-    `util.py <../gallery_dl/util.py>`__
 Description
-    Path to or name of an
-    `importable <https://docs.python.org/3/reference/import.html>`__
-    Python module whose namespace gets used as an alternative
-    |globals parameter|__
-    for compiled Python expressions.
+    | Path to or name of an
+      `importable <https://docs.python.org/3/reference/import.html>`__
+      Python module,
+    | whose namespace,
+      in addition to the ``GLOBALS`` dict in `util.py <../gallery_dl/util.py>`__,
+      gets used as |globals parameter|__ for compiled Python expressions.
 
 .. |globals parameter| replace:: ``globals`` parameter
 .. __: https://docs.python.org/3/library/functions.html#eval

gallery_dl/__init__.py

@@ -120,7 +120,7 @@ def main():
         # eval globals
         path = config.get((), "globals")
         if path:
-            util.GLOBALS = util.import_file(path).__dict__
+            util.GLOBALS.update(util.import_file(path).__dict__)
 
         # loglevels
         output.configure_logging(args.loglevel)