More escape sequence utilities

* Add `tmux-dcs-passthrough` to passthrough escape sequences tmux
  doesn't understand.
* Add `notify` to post a notification via the terminal emulator.

utilities/utilities.plugin.zsh

@@ -15,12 +15,29 @@ elif which xclip &> /dev/null; then
 fi
 
 # Abstract different ways to paste from the clipboard.
+# TODO: Use OSC-52 to get the clipboard, not widely supported though
 if [ "`uname`" = "Darwin" ]; then
+  # Use pbpaste to get the clipboard
   alias paste='pbpaste'
 elif which xclip &> /dev/null; then
+  # Use xclip to get the clipboard
   alias paste='xclip -selection c -o'
 fi
 
+# Passthrough an escape sequences tmux doesn't know about.
+tmux-dcs-passthrough() {
+  if [ -n "$TMUX" ]; then
+    printf "\x1bPtmux;\x1b$1\x1b\\"
+  else
+    printf "$1"
+  fi
+}
+
+# OSC 9 - Post a notification - supported by iTerm2, maybe others?
+notify() {
+  tmux-dcs-passthrough "\x1b]9;$*\x7"
+}
+
 # Detect the type and extract an archive file.
 extract() {
   if [ -f $1 ]; then