gen-env

# gen-env Skill Generate or review a `gen-env` command that enables running **multiple isolated instances** of a project on localhost simultaneously (e.g., multiple worktrees, feature branches, or versions). ## The Problem Without isolation, multiple instances of the same project: - Fight for hardcoded ports (3000, 5432, 8080) - Share Docker volumes → data corruption - Share browser cookies/localStorage → auth confusion - Have ambiguous container names → can't tell which is which - Risk catastrophic cleanup → `docker down -v` nukes everything ## The Solution: Instance Identity Everything flows from a **workspace name**: ``` name = "feature-x" ↓ ┌─────────────────────────────────────────────────────┐ │ COMPOSE_PROJECT_NAME = localnet-feature-x │ │ DOCKER_NETWORK = localnet-feature-x │ │ VOLUME_PREFIX = localnet-feature-x │ │ CONTAINER_PREFIX = localnet-feature-x- │ │ TILT_HOST = feature-x.localhost │ │ Ports = dynamically allocated │ │ URLs = derived from host + ports │ └─────────────────────────────────────────────────────┘ ``` ## Isolation Dimensions ### 1. Port Isolation Each instance gets unique ports from ephemeral range (49152-65535). ### 2. Data Isolation Docker Compose project name controls volume naming: - Instance A: `localnet-main_postgres_data` - Instance B: `localnet-feature-x_postgres_data` No cross-contamination. Independent dat...