A rough startup script for The Jolly Advisor - tested on a fresh ubuntu install, theoretically good for any debian system.

setup.sh

#!/bin/bash

# Check arguments
if [ $# -eq 0 ]; then
    echo Error: Please include your github username as an argument
    exit
fi

# Check package manager
which apt-get 2> /dev/null
if [ "$?" != "0" ]; then
    echo Error: non-debian systems are unsupported
    exit 1
fi

# Warning message
read -p "***** This script assumes that github.com/$1/the_jolly_advisor is a valid
repository - double check that before continuing.

This script will install Ruby (and ruby libraries), postgres, and
The Jolly Advisor onto your computer. It may take up to an hour. Are you sure
you want to proceed? [y/N]
" -r
echo   
if [[ ! $REPLY =~ ^[Yy]$ ]]
then
    exit 1
fi

which git 2> /dev/null
if [ "$?" != "0" ]; then
    sudo apt-get -y install git
fi

# The Jolly Advisor code
if [ -d "the_jolly_advisor" ]; then
    echo "*****We've determined that you've already installed The Jolly Advisor in
    the directory, so we're skipping that step."
else
    echo *****Obtaining The Jolly Advisor source code...
    git clone http://github.com/$1/the_jolly_advisor.git
fi

if [ "$?" != "0" ]; then
    echo "Error: Problem cloning the jolly advisor - is there a valid fork under the
    specified username?"
    exit 1
fi
cd the_jolly_advisor
echo
echo "*****Successfully obtained the jolly advisor."

# RVM and ruby
which rvm 2> /dev/null
if [ "$?" = "0" ]; then
    set -e
    echo "*****We've determined that you've already installed RVM, so we're skipping that step."
else
    set -e
    echo *****Installing RVM...
    gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
    \curl -sSL https://get.rvm.io | bash -s stable
    source $HOME/.rvm/scripts/rvm
fi

echo
echo "*****Installing Ruby 2.3.0..."
rvm install ruby-2.3.0
gem install bundler

# Postgres
echo
echo "*****Installing postgres..."
sudo apt-get -y install postgresql
echo
echo "*****Postgres has installed successfully. Please follow the steps below."
echo "Run \$ createuser --interactive"
echo "Follow the steps to create a privileged user, use your login
username."
echo "Run \$ createdb the_jolly_advisor_development; createdb the_jolly_advisor_test; exit"
sudo su - postgres
read -p "*****Did any errors occur while configuring postgres? [Y/n] " -r
if [[ ! $REPLY =~ ^[Nn]$ ]]
then
    exit 1
fi

# Bundle
## Sometimes the system will require libpq-dev to be installed first
echo
echo *****installing dependencies before bundling...
sudo apt-get install -y libpq-dev
echo
echo "*****Running bundle..."
bundle

# DB Migrations and rails
echo
echo "*****Migrating the DB and importing from SIS..."
rake db:migrate
rails r "require 'sis_importer';SISImporter.import_sis"

echo "*****The installer has completed successfully!
run \$ source $HOME/.rvm/scripts/rvm
and then start your local server with \$ rails s"

Instead of just telling them that you're assuming github.com/[USER]/the_jolly_advisor is valid, you could curl it

And then error if curl returns a 404

I'm not sure that rvm install xxx sets that as the active version right away, so gem on the next line might not be the version that rvm just installed

line 101 has a rake task. I think it's rake import_sis or something like that

Maybe allow users to specify a directory so it doesn't have to go to ~/the_jolly_advisor ?

Also, you should look into optparse for specifying options