[path] implement conditional 'part-directory' (#8329)

gallery_dl/downloader/common.py

@@ -31,8 +31,15 @@ class DownloaderBase():
         self.partdir = self.config("part-directory")
 
         if self.partdir:
-            self.partdir = util.expand_path(self.partdir)
-            os.makedirs(self.partdir, exist_ok=True)
+            if isinstance(self.partdir, dict):
+                self.partdir = [
+                    (util.compile_filter(expr) if expr else util.true,
+                     util.expand_path(pdir))
+                    for expr, pdir in self.partdir.items()
+                ]
+            else:
+                self.partdir = util.expand_path(self.partdir)
+                os.makedirs(self.partdir, exist_ok=True)
 
         proxies = self.config("proxy", util.SENTINEL)
         if proxies is util.SENTINEL:

gallery_dl/path.py

@@ -325,7 +325,15 @@ class PathFormat():
             self.kwdict["extension"] = self.prefix + self.extension_map(
                 "part", "part")
             self.build_path()
-        if part_directory:
+
+        if part_directory is not None:
+            if isinstance(part_directory, list):
+                for condition, part_directory in part_directory:
+                    if condition(self.kwdict):
+                        break
+                else:
+                    return
+
             self.temppath = os.path.join(
                 part_directory,
                 os.path.basename(self.temppath),