Add shell.sh utility to run nested X11/wayland sessions

Runs X11 by default, pass in -w to run a wayland session. The dbus address is
copied to clipboard, so it's easy to connect to the new sesssion from emacs
using `gnome-shell-set-dbus-address`.

Depends on Xephyr in the case of x11, and xclip is used to copy the dbus
address.

shell.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+
+# Simple helper script to start nested wayland/x11 gnome sessions
+
+# The new dbus address is copied into the clipboard so you're able to run
+# `M-x # gnome-shell-set-dbus-address` and paste the address.
+
+old_display=$DISPLAY
+
+d=0
+while [ -e /tmp/.X11-unix/X${d} ]; do
+    d=$((d + 1))
+done
+
+NEW_DISPLAY=:$d
+
+export XDG_CONFIG_HOME=$HOME/paperwm/.config
+
+args=()
+
+DISPLAY=$NEW_DISPLAY
+eval $(dbus-launch --exit-with-session --sh-syntax)
+echo $DBUS_SESSION_BUS_ADDRESS
+
+echo -n $DBUS_SESSION_BUS_ADDRESS \
+    | DISPLAY=$old_display xclip -i -selection clipboard
+
+DISPLAY=$old_display
+case $1 in
+    w*|-w*|--w*)
+        echo "Running Wayland Gnome Shell"
+        args=(--nested --wayland)
+        ;;
+    *)
+        echo "Running X11 Gnome Shell"
+        Xephyr $NEW_DISPLAY &
+        DISPLAY=$NEW_DISPLAY
+        args=--x11
+        ;;
+esac
+
+
+dconf write /org/gnome/shell/enabled-extensions "['paperwm@hedning:matrix.org]"
+
+gnome-shell $args &
+