Allow explicitly setting None

Signed-off-by: Kenji Miyake <kmiyake@applied.co>

Author: kenji-miyake-ai

jinja2cli/cli.py

@@ -370,6 +370,9 @@ def cli(opts, args):
 def parse_kv_string(pairs):
     dict_ = {}
     for pair in pairs:
+        if "=" not in pair:
+            dict_[force_text(pair)] = None
+            continue
         k, v = pair.split("=", 1)
         dict_[force_text(k)] = force_text(v)
     return dict_