Script to clone or init a repository in a git-worktree setup

gitwt.sh

#!/bin/zsh

# Usage:
#   gitwt -c <git-uri>                        Clone an existing repo into a worktree setup
#   gitwt -n <project-name>                   Create a new project from scratch with worktree setup
#   gitwt -b <branch-name> [<base-branch>]    Create a new worktree with a new branch (run from project root)
#                                             Optionally base the new branch on <base-branch>. Pass it exactly as you
#                                             want git to resolve it (e.g. 'develop' for the local branch, or
#                                             'origin/develop' for the remote-tracking ref). If omitted, git's default
#                                             behavior applies (branch from HEAD).
#   gitwt <branch-name>                       Create a worktree for an existing branch (run from project root)
#
# Examples:
#   gitwt -c git@github.com:commercetools/the-repo-i-want-to-clone.git
#   gitwt -n my-new-project
#   gitwt -b my-feature-branch
#   gitwt -b my-feature-branch develop
#   gitwt -b my-feature-branch origin/develop
#   gitwt some-existing-branch

set -euo pipefail

function usage() {
  echo "Usage:"
  echo "  gitwt -c <git-uri>                       Clone a repo into a worktree setup"
  echo "  gitwt -n <project-name>                  Create a new project with worktree setup"
  echo "  gitwt -b <branch-name> [<base-branch>]   Create a new worktree with a new branch"
  echo "                                           (optionally based on <base-branch>, passed as-is to git;"
  echo "                                           if omitted, git branches from HEAD)"
  echo "  gitwt <branch-name>                      Create a worktree for an existing branch"
  echo ""
  echo "Examples:"
  echo "  gitwt -c git@github.com:org/repo.git"
  echo "  gitwt -n my-new-project"
  echo "  gitwt -b my-feature-branch"
  echo "  gitwt -b my-feature-branch develop"
  echo "  gitwt -b my-feature-branch origin/develop"
  echo "  gitwt some-existing-branch"
}

function check_dir() {
  local name="$1"
  if [[ -d "$name" ]]; then
    echo "Error: directory '$name' already exists"
    exit 1
  fi
}

function link_bare() {
  echo "gitdir: ./.bare" > .git
  git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
}

function create_project() {
  local project_name="$1"
  local default_branch="main"
  local worktree_dir="${project_name}_${default_branch}"

  check_dir "$project_name"

  echo "Creating new worktree project '$project_name'..."

  mkdir "$project_name"
  cd "$project_name"

  git init --bare .bare

  link_bare

  git worktree add "$worktree_dir" -b "$default_branch"

  echo ""
  echo "Done! Your worktree project is ready:"
  echo "  $project_name/"
  echo "    .bare/            (git database)"
  echo "    .git              (pointer to .bare)"
  echo "    $worktree_dir/    (worktree on $default_branch branch)"
  echo ""
  echo "Next steps:"
  echo "  cd $project_name/$worktree_dir"
  echo "  have fun!"
}

function clone_repo() {
  local uri="$1"

  # Extract repo name from URI
  # Handles both SSH (git@github.com:org/repo.git) and HTTPS (https://github.com/org/repo.git)
  local repo_name="${uri:t:r}"

  if [[ -z "$repo_name" ]]; then
    echo "Error: could not extract repository name from '$uri'"
    exit 1
  fi

  check_dir "$repo_name"

  echo "Setting up bare worktree repo for '$repo_name'..."

  mkdir "$repo_name"
  cd "$repo_name"

  git clone --bare "$uri" .bare

  link_bare

  local default_branch=$(git -C .bare symbolic-ref --short HEAD)
  local worktree_dir="${repo_name}_${default_branch}"

  git worktree add "$worktree_dir" "$default_branch"
  git branch --set-upstream-to="origin/$default_branch" "$default_branch"

  echo ""
  echo "Done! Your worktree repo is ready:"
  echo "  $repo_name/"
  echo "    .bare/            (git database)"
  echo "    .git              (pointer to .bare)"
  echo "    $worktree_dir/    (worktree on $default_branch branch)"
  echo ""
  echo "Next steps:"
  echo "  cd $repo_name/$worktree_dir"
  echo "  have fun!"
}

function create_branch_worktree() {
  local branch_name="$1"
  local base_branch="${2:-}"

  if [[ ! -d ".bare" ]]; then
    echo "Error: not inside a gitwt project (no .bare directory found)"
    exit 1
  fi

  local worktree_dir="${branch_name}"

  check_dir "$worktree_dir"

  echo "Fetching origin..."
  git fetch origin

  if [[ -n "$base_branch" ]]; then
    echo "Creating worktree for branch '$branch_name' based on '$base_branch'..."
    git worktree add "$worktree_dir" -b "$branch_name" "$base_branch"
  else
    echo "Creating worktree for branch '$branch_name'..."
    git worktree add "$worktree_dir" -b "$branch_name"
  fi

  echo ""
  echo "Done! New worktree ready:"
  if [[ -n "$base_branch" ]]; then
    echo "  $worktree_dir/    (worktree on $branch_name branch, based on $base_branch)"
  else
    echo "  $worktree_dir/    (worktree on $branch_name branch)"
  fi
}

function checkout_branch_worktree() {
  local branch_name="$1"

  if [[ ! -d ".bare" ]]; then
    echo "Error: not inside a gitwt project (no .bare directory found)"
    exit 1
  fi

  local worktree_dir="${branch_name}"

  check_dir "$worktree_dir"

  echo "Fetching origin..."
  git fetch origin

  echo "Creating worktree for existing branch '$branch_name'..."
  git worktree add "$worktree_dir" "$branch_name"

  echo ""
  echo "Done! New worktree ready:"
  echo "  $worktree_dir/    (worktree on $branch_name branch)"
}

# --- Main ---

if [[ $# -eq 2 && "$1" == "-b" ]]; then
  create_branch_worktree "$2"
elif [[ $# -eq 3 && "$1" == "-b" ]]; then
  create_branch_worktree "$2" "$3"
elif [[ $# -eq 2 && "$1" == "-n" ]]; then
  create_project "$2"
elif [[ $# -eq 2 && "$1" == "-c" ]]; then
  clone_repo "$2"
elif [[ $# -eq 1 && "$1" != -* ]]; then
  checkout_branch_worktree "$1"
else
  usage
  exit 1
fi