[facebook] add 'loop' option (#8696)

docs/configuration.rst

@@ -3021,6 +3021,16 @@ Note
     It is possible to use ``"all"`` instead of listing all values separately.
 
 
+extractor.facebook.loop
+-----------------------
+Type
+    ``bool``
+Default
+    ``false``
+Description
+    Continue when detecting a jump to a set's beginning.
+
+
 extractor.facebook.videos
 -------------------------
 Type

docs/gallery-dl.conf

@@ -334,6 +334,7 @@
 
             "author-followups": false,
             "include": "photos",
+            "loop"   : false,
             "videos" : true
         },
         "fanbox":

gallery_dl/extractor/facebook.py

@@ -306,6 +306,12 @@ class FacebookExtractor(Extractor):
                         "Detected a loop in the set, it's likely finished. "
                         "Extraction is over."
                     )
+            elif int(photo["next_photo_id"]) > int(photo["id"]) + i*120:
+                self.log.info(
+                    "Detected jump to the beginning of the set. (%s -> %s)",
+                    photo["id"], photo["next_photo_id"])
+                if self.config("loop", False):
+                    all_photo_ids.append(photo["next_photo_id"])
             else:
                 all_photo_ids.append(photo["next_photo_id"])