Bash script to generate an edge-Rails app.

rails_edge

#!/bin/sh
#
# Generates an edge-Rails application.

if [ $# -eq 0 ]
then
  echo "usage: rails_edge <name>"
  exit 1
fi

name=$1
mkdir $name
cd $name

# Create a Gemfile that tells bundler to install
# the `rails` gem from the GitHub source.

rails_gem="gem 'rails', github: 'rails/rails'"

cat > Gemfile << EOF
source 'https://rubygems.org'

ruby '3.0.2'

$rails_gem
EOF

bundle install

# Generate a new Rails app in the current directory using the
# latest development version (--dev).

bundle exec rails new . --dev --force

# Update the Gemfile so the `rails` dependency points at GitHub
# again rather than the local filesystem.

escaped_rails_gem=$(printf '%s\n' "$rails_gem" | sed -e 's/[\/&]/\\&/g')
sed -i '' -e 's/.*gem "rails".*/'"$escaped_rails_gem"'/g' Gemfile

bundle install

bundle exec rails s