a bootstrapping script to support a one-line install command

based on a script by @jkaberg in #141

setup/bootstrap.sh

+#!/bin/bash
+#########################################################
+# This script is intended to be run like this:
+#
+#   wget https://raw.githubusercontent.com/mail-in-a-box/mailinabox/master/setup/bootstrap.sh
+#   sudo bash bootstrap.sh
+#
+# We can't pipe directly to bash because setup/start.sh
+# asks for user input on stdin.
+#
+#########################################################
+
+# Are we running as root?
+if [[ $EUID -ne 0 ]]; then
+	echo "This script must be run as root. Did you leave out sudo?"
+	exit
+fi
+
+# Go to root's home directory.
+cd
+
+# Clone the Mail-in-a-Box repository if it doesn't exist.
+if [ ! -d mailinabox ]; then
+	echo Downloading Mail-in-a-Box . . .
+	apt-get -q -q install -y git
+	git clone -q --depth 1 -b master https://github.com/mail-in-a-box/mailinabox
+	cd mailinabox
+
+# If it does exist, update it.
+else
+	echo Updating Mail-in-a-Box . . .
+	cd mailinabox
+	if ! git pull -q --ff-only; then
+		echo "Update failed. Did you modify something in `pwd`?"
+		exit
+	fi
+fi
+
+# Start setup script.
+setup/start.sh