trim — zsh function to delete local git branches (+ worktrees) that have been merged. Catches both true merges and squash merges via GitHub PR status. Auto-detects default branch from origin/HEAD.

git-trim-merged-branches-and-worktrees.zsh

# Delete local branches merged to the default branch + their worktrees
# Catches both true merges (git) and squash merges (GitHub PR status)
# Reads default branch from origin/HEAD — works with main, staging, etc.
# Usage: trim [--force]  (--force skips confirmation)
trim() {
  local repo_root
  repo_root="$(git rev-parse --show-toplevel 2>/dev/null)" || { echo "Not in a git repo"; return 1; }

  local base_branch
  base_branch="$(git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null)"
  base_branch="${base_branch##refs/remotes/origin/}"
  if [[ -z "$base_branch" ]]; then
    echo "Cannot determine default branch. Run: git remote set-head origin --auto"
    return 1
  fi

  git fetch origin "$base_branch" --quiet

  # 1) Branches merged via git (fast-forward / true merge)
  local -A to_delete=()
  local branch
  while IFS= read -r branch; do
    branch="${branch//[[:space:]]/}"
    branch="${branch#+}"
    [[ -z "$branch" || "$branch" == "$base_branch" || "$branch" == "main" || "$branch" == \** ]] && continue
    to_delete[$branch]=git
  done < <(git branch --merged "origin/$base_branch")

  # 2) Branches whose GitHub PR was squash-merged
  local -a local_branches=()
  while IFS= read -r branch; do
    branch="${branch//[[:space:]]/}"
    branch="${branch#+}"
    [[ -z "$branch" || "$branch" == "$base_branch" || "$branch" == "main" || "$branch" == \** ]] && continue
    local_branches+=("$branch")
  done < <(git branch)

  if [[ ${#local_branches[@]} -gt 0 ]]; then
    local -A merged_prs=()
    while IFS= read -r branch; do
      [[ -n "$branch" ]] && merged_prs[$branch]=1
    done < <(gh pr list --state merged --limit 200 --json headRefName --jq '.[].headRefName' 2>/dev/null)

    for branch in "${local_branches[@]}"; do
      if [[ -n "${merged_prs[$branch]+x}" && -z "${to_delete[$branch]+x}" ]]; then
        to_delete[$branch]=squash
      fi
    done
  fi

  if [[ ${#to_delete} -eq 0 ]]; then
    echo "No merged branches to clean up."
    git worktree prune
    return 0
  fi

  # Build worktree map
  local wt_info wt_path answer
  wt_info="$(git worktree list --porcelain)"

  echo "Branches to delete (${#to_delete} total):"
  for branch in "${(@k)to_delete}"; do
    wt_path=$(echo "$wt_info" | awk -v b="refs/heads/${branch}" '/^worktree /{wt=$2} /^branch /{if($2==b)print wt}')
    local label="[${to_delete[$branch]}]"
    if [[ -n "$wt_path" ]]; then
      echo "  $label $branch  →  $wt_path"
    else
      echo "  $label $branch"
    fi
  done

  if [[ "$1" != "--force" ]]; then
    echo ""
    read "answer?Proceed? [y/N] "
    [[ "$answer" =~ ^[Yy]$ ]] || { echo "Aborted."; return 0; }
  fi

  local count=0
  for branch in "${(@k)to_delete}"; do
    wt_path=$(echo "$wt_info" | awk -v b="refs/heads/${branch}" '/^worktree /{wt=$2} /^branch /{if($2==b)print wt}')
    if [[ -n "$wt_path" && -d "$wt_path" ]]; then
      echo "Removing worktree: $wt_path"
      rm -rf "$wt_path"
    fi
    git branch -D "$branch" 2>/dev/null
    (( count++ ))
  done

  git worktree prune
  echo "Done. Cleaned $count branch(es)."
}