If there is one thing which makes coding with AI go from being a helper to being an entire development process, it\u2019s the use of independent workable copies of your code. And what I mean by that is: being able to work on multiple features or ideas at once, independently, without breaking anything \u2014 because your environments are so isolated that it\u2019s a breeze to use AI for your agentic development process.<\/p>\n\n
This is a How To guide where I show you how I use git worktrees and isolated Ruby on Rails environments to enable independent coding using Claude Code<\/a>.<\/p>\n\n Before we start, let me explain what tools are required to set this up:<\/p>\n\n I assume you\u2019re familiar with Rails development and how to install Claude Code. The new piece here is git worktrees. Think of them like this: instead of cloning the repo twice, you create a second working directory that points at the same repository. Both directories see the same branches, commits and history \u2014 but each one has its own checked-out branch and its own working files. That\u2019s the foundation for everything below.<\/p>\n\n The first change is your mindset. Don\u2019t think of this as simply \u201cfeature branches\u201d \u2014 think of each worktree as an independent developer working on your project. You\u2019re the orchestrator.<\/p>\n\n The most basic way of using worktrees is Strip out all hardcoded database names and make everything environment-driven:<\/p>\n\n Now each worktree can point at its own database just by setting All worktrees share the same Postgres and Redis instances \u2014 they just use different database names and Redis DB numbers. If you\u2019re running them locally, you\u2019re already set. If you prefer Docker, here\u2019s a simple The non-default ports (5431\/6380) avoid collisions with any locally installed Postgres or Redis. Adjust to match your setup \u2014 the important thing is that every worktree talks to the same services but uses a different database name and Redis DB number.<\/p>\n\n This is the core trick. A Directory The Procfile just references The required tooling<\/h3>\n\n
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.git<\/code> history. If you already have git installed, you already have worktrees. No extra install needed.<\/li>\n The changes<\/h3>\n\n
git worktree add ..\/my-feature feature-branch<\/code>. But your codebase isn\u2019t ready for that kind of independence yet. Each worktree needs its own database, its own port, and its own Redis namespace. Let\u2019s fix that.<\/p>\n\na) ENV-driven database.yml<\/h4>\n\n
default<\/span>:<\/span> &default<\/span>\n adapter<\/span>:<\/span> postgresql<\/span>\n encoding<\/span>:<\/span> unicode<\/span>\n database<\/span>:<\/span> \n username<\/span>:<\/span> \n password<\/span>:<\/span> \n host<\/span>:<\/span> \n port<\/span>:<\/span> \n pool<\/span>:<\/span> 5<\/span>\n\ndevelopment<\/span>:<\/span>\n <<<\/span>:<\/span> *default<\/span>\n\ntest<\/span>:<\/span>\n <<<\/span>:<\/span> *default<\/span>\n<\/code><\/pre><\/div><\/div>\n\nDATABASE_NAME<\/code>.<\/p>\n\nb) Shared Postgres & Redis<\/h4>\n\n
docker-compose.yml<\/code>:<\/p>\n\nservices<\/span>:<\/span>\n db<\/span>:<\/span>\n image<\/span>:<\/span> postgres:17-alpine<\/span>\n volumes<\/span>:<\/span>\n -<\/span> db_data:\/var\/lib\/postgresql\/data<\/span>\n environment<\/span>:<\/span>\n POSTGRES_USER<\/span>:<\/span> postgres<\/span>\n POSTGRES_PASSWORD<\/span>:<\/span> password<\/span>\n ports<\/span>:<\/span>\n -<\/span> \"<\/span>${DOCKER_POSTGRES_PORT:-5431}:5432\"<\/span>\n\n redis<\/span>:<\/span>\n image<\/span>:<\/span> redis:7-alpine<\/span>\n command<\/span>:<\/span> redis-server<\/span>\n ports<\/span>:<\/span>\n -<\/span> \"<\/span>${DOCKER_REDIS_PORT:-6380}:6379\"<\/span>\n\nvolumes<\/span>:<\/span>\n db_data<\/span>:<\/span>\n<\/code><\/pre><\/div><\/div>\n\nc) Auto-derive environment per worktree<\/h4>\n\n
bin\/worktree-env<\/code> script reads the directory name and derives all the environment variables from it. Let\u2019s say your app is called myapp<\/code>:<\/p>\n\n#!\/usr\/bin\/env bash<\/span>\nWORKTREE_NAME<\/span>=<\/span>$(<\/span>basename<\/span> \"<\/span>$PWD<\/span>\"<\/span>)<\/span>\nWORKTREE_SUFFIX<\/span>=<\/span>$(<\/span>echo<\/span> \"<\/span>$WORKTREE_NAME<\/span>\"<\/span> | sed<\/span> 's\/^myapp-*\/\/'<\/span> | sed<\/span> 's\/-\/_\/g'<\/span>)<\/span>\n\nif<\/span> [<\/span> -z<\/span> \"<\/span>$WORKTREE_SUFFIX<\/span>\"<\/span> ]<\/span> ||<\/span> [<\/span> \"<\/span>$WORKTREE_SUFFIX<\/span>\"<\/span> =<\/span> \"myapp\"<\/span> ]<\/span>;<\/span> then<\/span>\n # Main worktree<\/span>\n DATABASE_NAME<\/span>=<\/span>\"<\/span>${<\/span>DATABASE_NAME<\/span>:-<\/span>myapp_development<\/span>}<\/span>\"<\/span>\n PORT<\/span>=<\/span>\"<\/span>${<\/span>PORT<\/span>:-<\/span>3000<\/span>}<\/span>\"<\/span>\n REDIS_DB<\/span>=<\/span>\"<\/span>${<\/span>REDIS_DB<\/span>:-<\/span>1<\/span>}<\/span>\"<\/span>\nelse<\/span>\n # Feature worktree \u2014 derive everything from the directory name<\/span>\n DATABASE_NAME<\/span>=<\/span>\"<\/span>${<\/span>DATABASE_NAME<\/span>:-<\/span>myapp_<\/span>${<\/span>WORKTREE_SUFFIX<\/span>}<\/span>_development<\/span>}<\/span>\"<\/span>\n PORT<\/span>=<\/span>$((<\/span> 3001<\/span> +<\/span> $(<\/span>echo<\/span> \"<\/span>$WORKTREE_SUFFIX<\/span>\"<\/span> | cksum<\/span> | cut<\/span> -d<\/span>' '<\/span> -f1<\/span>)<\/span> %<\/span> 99<\/span> ))<\/span>\n REDIS_DB<\/span>=<\/span>$((<\/span> $(<\/span>echo<\/span> \"<\/span>$WORKTREE_SUFFIX<\/span>\"<\/span> | cksum<\/span> | cut<\/span> -d<\/span>' '<\/span> -f1<\/span>)<\/span> %<\/span> 15<\/span> +<\/span> 1<\/span> ))<\/span>\nfi\n\n<\/span>echo<\/span> \"export DATABASE_NAME='<\/span>$DATABASE_NAME<\/span>'\"<\/span>\necho<\/span> \"export PORT='<\/span>$PORT<\/span>'\"<\/span>\necho<\/span> \"export REDIS_URL='redis:\/\/localhost:<\/span>${<\/span>REDIS_PORT<\/span>:-<\/span>6379<\/span>}<\/span>\/<\/span>$REDIS_DB<\/span>'\"<\/span>\n<\/code><\/pre><\/div><\/div>\n\nmyapp-feature-auth<\/code> \u2192 database myapp_feature_auth_development<\/code>, port 3042<\/code> (or whatever the hash lands on), Redis DB 7<\/code>. Fully deterministic, no manual config.<\/p>\n\nd) Procfile.dev<\/h4>\n\n
${PORT}<\/code> so each worktree starts on its own port:<\/p>\n\n