Document {url} and {url:pretty} for :set-cmd-text

doc/help/commands.asciidoc

@@ -650,6 +650,8 @@ Syntax: +:set-cmd-text [*--space*] [*--append*] 'text'+
 
 Preset the statusbar to some text.
 
+You can use the `{url}` and `{url:pretty}` variables here which will get replaced by the encoded/decoded URL.
+
 ==== positional arguments
 * +'text'+: The commandline to set.
 

qutebrowser/mainwindow/statusbar/command.py

@@ -95,6 +95,9 @@ class Command(misc.MinimalLineEditMixin, misc.CommandLineEdit):
     def set_cmd_text_command(self, text, space=False, append=False):
         """Preset the statusbar to some text.
 
+        You can use the `{url}` and `{url:pretty}` variables here which will get
+        replaced by the encoded/decoded URL.
+
         //
 
         Wrapper for set_cmd_text to check the arguments and allow multiple