properly update the config-dictionary

When using 2 or more config files, the values of the second would
improperly overwrite nested dictionaries of the first one.
The new method properly combines these nested dictionaries as well.

gallery_dl/config.py

@@ -12,6 +12,7 @@ import sys
 import json
 import os.path
 import logging
+from . import util
 
 log = logging.getLogger("config")
 
@@ -57,7 +58,10 @@ def load(*files, format="json", strict=False):
             path = os.path.expanduser(os.path.expandvars(conf))
             with open(path) as file:
                 confdict = parsefunc(file)
-            _config.update(confdict)
+            if not _config:
+                _config.update(confdict)
+            else:
+                util.combine_dict(_config, confdict)
         except FileNotFoundError:
             if strict:
                 log.error("Configuration file '%s' not found", path)

gallery_dl/extractor/deviantart.py

@@ -311,7 +311,7 @@ class DeviantartJournalExtractor(DeviantartExtractor):
                r"/(?:journal|blog)/?(?:\?catpath=/)?$"]
     test = [
         ("http://shimoda7.deviantart.com/journal/", {
-            "url": "f7960ae06e774d6931c61ad309c95a10710658b2",
+            "url": "b1a3460e7da0f34c8f6c286a3b5428fd4d3bc64b",
             "keyword": "6444966c703e63470a5fdd8f460993b68955c32c",
         }),
         ("http://shimoda7.deviantart.com/journal/?catpath=/", None),

gallery_dl/util.py

@@ -80,6 +80,15 @@ def bdecode(data, alphabet="0123456789"):
     return num
 
 
+def combine_dict(a, b):
+    """Recursively combine the contents of b into a"""
+    for key, value in b.items():
+        if key in a and isinstance(value, dict) and isinstance(a[key], dict):
+            combine_dict(a[key], value)
+        else:
+            a[key] = value
+
+
 def code_to_language(code, default=None):
     """Map an ISO 639-1 language code to its actual name"""
     return CODES.get((code or "").lower(), default)