git-fork

#!/usr/bin/env bash
set -euo pipefail

GH_USERNAME="${1:-gonzaloserrano}"

# Ensure we are inside a git repo
if [ ! -f ".git/config" ]; then
  echo "No .git/config found. Run this inside a git repository." >&2
  exit 1
fi

# Ensure origin exists
if ! git config --get remote.origin.url >/dev/null 2>&1; then
  echo "No 'origin' remote found in this repo." >&2
  exit 1
fi

# If fork already exists, do nothing (except print config)
if git config --get remote.fork.url >/dev/null 2>&1; then
  echo "Remote 'fork' already exists. Nothing to do."
  echo
  cat .git/config
  exit 0
fi

origin_url="$(git config --get remote.origin.url)"
origin_url="${origin_url%/}"  # strip trailing slash

# Build fork URL based on origin URL
case "$origin_url" in
  git@github.com:*)
    # SSH form: git@github.com:ORG/REPO(.git)
    repo_path="${origin_url#git@github.com:}"  # ORG/REPO(.git)
    repo_name="${repo_path#*/}"               # REPO(.git)
    fork_url="git@github.com:${GH_USERNAME}/${repo_name}"
    ;;
  https://github.com/*)
    # HTTPS form: https://github.com/ORG/REPO(.git)
    repo_path="${origin_url#https://github.com/}"  # ORG/REPO(.git)
    repo_name="${repo_path#*/}"                    # REPO(.git)
    fork_url="https://github.com/${GH_USERNAME}/${repo_name}"
    ;;
  *)
    echo "Unsupported origin URL format: $origin_url" >&2
    exit 1
    ;;
esac

# Check if fork exists on GitHub, create if not
org_name="${repo_path%%/*}"
repo_base="${repo_name%.git}"  # strip .git suffix if present
if ! gh repo view "${GH_USERNAME}/${repo_base}" >/dev/null 2>&1; then
  echo "Fork ${GH_USERNAME}/${repo_base} does not exist on GitHub."
  read -rp "Create it? [y/N] " answer
  if [[ "$answer" =~ ^[Yy]$ ]]; then
    gh repo fork "${org_name}/${repo_base}" --remote=false
  else
    echo "Aborted."
    exit 1
  fi
fi

# Add the fork remote
git remote add fork "$fork_url"

# Ensure the desired fetch refspec
git config remote.fork.fetch "+refs/heads/*:refs/remotes/fork/*"

# Print resulting config
echo
cat .git/config