[sankaku] support '/posts/' tag search URLs (#4740)

gallery_dl/extractor/sankaku.py

@@ -87,7 +87,7 @@ class SankakuTagExtractor(SankakuExtractor):
     subcategory = "tag"
     directory_fmt = ("{category}", "{search_tags}")
     archive_fmt = "t_{search_tags}_{id}"
-    pattern = BASE_PATTERN + r"/?\?([^#]*)"
+    pattern = BASE_PATTERN + r"(?:/posts)?/?\?([^#]*)"
     example = "https://sankaku.app/?tags=TAG"
 
     def __init__(self, match):

test/results/sankaku.py

@@ -53,6 +53,20 @@ __tests__ = (
     "#class"   : sankaku.SankakuTagExtractor,
 },
 
+{
+    "#url"     : "https://chan.sankakucomplex.com/posts?tags=TAG",
+    "#comment" : "'/posts' in tag search URL (#4740)",
+    "#category": ("booru", "sankaku", "tag"),
+    "#class"   : sankaku.SankakuTagExtractor,
+},
+
+{
+    "#url"     : "https://chan.sankakucomplex.com/ja/posts/?tags=あえいおう",
+    "#comment" : "'/posts' in tag search URL (#4740)",
+    "#category": ("booru", "sankaku", "tag"),
+    "#class"   : sankaku.SankakuTagExtractor,
+},
+
 {
     "#url"     : "https://chan.sankakucomplex.com/?tags=bonocho+a+b+c+d",
     "#comment" : "error on five or more tags",