docs: show a note about argument expansion

Author: loichyan

bin/proxy

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
 set -eo pipefail
 # Use `tmux display` to ensure we see the latest environments.
-IFS=':' read -r _ caller < <(tmux display -p '#{__tmux_popup_caller}')
+IFS=':' read -r _ caller < <(tmux display-message -p '#{__tmux_popup_caller}')
 TMUX=${caller:-$TMUX} exec tmux "$@"

src/toggle.sh

@@ -17,6 +17,10 @@ usage() {
 
 		  toggle.sh [OPTIONS] [POPUP_OPTIONS] [SHELL_COMMAND]...
 
+		  Note that every argument will be expanded as a tmux format string
+		  before it is parsed. To avoid unexpected expansion of certain format
+		  strings, escape them with `##{<format string>}`.
+
 		Options:
 
 		  --name <name>               Popup name [Default: "$DEFAULT_NAME"]