support accessing the current local datetime in format strings

{_now}, {_now:%Y-%m-%d}, etc
(#1968)

gallery_dl/formatter.py

@@ -12,12 +12,16 @@ import os
 import json
 import string
 import _string
+import datetime
 import operator
 from . import text, util
 
 _CACHE = {}
-_GLOBALS = {"_env": os.environ}
 _CONVERSIONS = None
+_GLOBALS = {
+    "_env": lambda: os.environ,
+    "_now": datetime.datetime.now,
+}
 
 
 def parse(format_string, default=None):
@@ -60,7 +64,7 @@ class StringFormatter():
     - "j". calls json.dumps
     - "t": calls str.strip
     - "d": calls text.parse_timestamp
-    - "U": calls urllib.parse.unquote
+    - "U": calls urllib.parse.unescape
     - "S": calls util.to_string()
     - "T": calls util.to_timestamü()
     - Example: {f!l} -> "example"; {f!u} -> "EXAMPLE"
@@ -147,7 +151,7 @@ class StringFormatter():
     def _apply_globals(self, gobj, funcs, fmt):
         def wrap(_):
             try:
-                obj = gobj
+                obj = gobj()
                 for func in funcs:
                     obj = func(obj)
             except Exception:
@@ -164,7 +168,7 @@ class StringFormatter():
         def wrap(kwdict):
             for key, funcs in lst:
                 try:
-                    obj = _GLOBALS[key] if key in _GLOBALS else kwdict[key]
+                    obj = _GLOBALS[key]() if key in _GLOBALS else kwdict[key]
                     for func in funcs:
                         obj = func(obj)
                     if obj: