_git-tag-version

#compdef git-tag-version
# zsh completion for git-tag-version

_git-tag-version () {
	_arguments -S -s "-h[usage]" "1:version-name" "2:from:__git_commits" "3:to:__git_commits"
}

git-tag-version

#!/usr/bin/env bash
#
# git helper for creating version tags with the message body containing the log of
# commits since the last tag
#
# (c) 2021 Maddison Hellstrom <github.com/b0o>, MIT License

set -eof pipefail

function main() {
  if [[ $1 =~ (-h|--help) ]]; then
    echo "usage: $(basename "$0") [version-name] [from] [to]" >&2
    return 1
  fi
  git status > /dev/null

  local v
  v="${1:-$(git show --quiet --format=%s HEAD)}"

  local from="${2:+^$2}"
  from="${from#\^-}"
  from="${from#\^\=}"
  from="${from:-$(
    cat \
      <(git rev-list --max-parents=0 HEAD | head -1) \
      <(git tag --list --sort=v:refname --format="%(object)" | xargs --no-run-if-empty printf '^%s\n') \
      | tail -1
  )}"

  local to="${3:-}"
  to="${to#-}"
  to="${to:-HEAD}"

  if [[ -n $(git tag --list --points-at="$to") ]]; then
    echo "error: already a tag: $to"
    return 1
  fi

  if git merge-base --is-ancestor "$to" "${from/\^/}"; then
    echo "error: $to is not an ancestor of $from"
    return 1
  fi

  local msg
  msg="$(git log --format="%cs  %h  %s" "${from}" "${to}^")"

  local comment
  mapfile -t comment << EOF
version: $v
from:    $from
to:      $to ($(git log --format=format:%s --max-count=1 "${to/\^/}"))

$(git log --format=short --decorate "$from" "$to" | paste -d' ' - <(echo "<--- TARGET ($v)"))

--

$(git tag --points-at="${from/\^/}" | head -1 | xargs --no-run-if-empty git log --max-count=1 --format=short --decorate)
EOF

  git tag --edit -sm "$v" -m "$msg$(echo; echo; printf '%s\n' "${comment[@]}" | sed 's/^/# /; s/\s*$//')" "$v" "$to"
}

main "$@"