add 'category-transfer' option

[ci skip]

docs/configuration.rst

@@ -245,6 +245,17 @@ Description Default value used for missing or undefined keyword names in
 =========== =====
 
 
+extractor.*.category-transfer
+-----------------------------
+=========== =====
+Type        ``bool``
+Default     Extractor-specific
+Description Transfer an extractor's (sub)category values to all child
+            extractors spawned by it, to let them inherit their parent's
+            config options.
+=========== =====
+
+
 extractor.*.archive
 -------------------
 =========== =====

gallery_dl/job.py

@@ -37,7 +37,8 @@ class Job():
             "chapter", [], False)
 
         # category transfer
-        if parent and parent.extractor.categorytransfer:
+        if parent and parent.extractor.config(
+                "category-transfer", parent.extractor.categorytransfer):
             self.extractor.category = parent.extractor.category
             self.extractor.subcategory = parent.extractor.subcategory