Add command line option to forget config on exit.

By default, Electrum saves the last opened wallet's path as well as
recently opened wallets.

This can be damaging to plausible deniability.

Now it's possible to run Electrum with `--forgetconfig` to not
write to the config at all, which includes the wallet paths.

electrum/commands.py

@@ -1171,6 +1171,7 @@ def add_global_options(parser):
 
 def add_wallet_option(parser):
     parser.add_argument("-w", "--wallet", dest="wallet_path", help="wallet path")
+    parser.add_argument("--forgetconfig", action="store_true", dest="forget_config", default=False, help="Forget config on exit")
 
 def get_parser():
     # create main parser

electrum/simple_config.py

@@ -226,6 +226,8 @@ class SimpleConfig(Logger):
         return key not in self.cmdline_options
 
     def save_user_config(self):
+        if self.get('forget_config'):
+            return
         if not self.path:
             return
         path = os.path.join(self.path, "config")