TODO list for any git branch. Read file header for installation and usage.

git-todo.bash

#!/usr/bin/env bash
# Brief: TODO list specific to git branches. No effect on commits, staged or worktree
# Installation:
#   chmod +x ./git-todo
#   sudo mv ./git-todo /usr/local/bin
#   git config --global alias.todo '!git-todo'
# Help: git todo -h
# Author: Somajit Dey <dey.somajit@gmail.com> 2021 [https://github.com/SomajitDey]
# Source: https://gist.github.com/SomajitDey
# GitHubGist Search Terms: username:SomajitDey filename:git-todo.bash

usage(){
echo " Brief: TODO list specific to given git branch. If branch is not given, current branch is used.
 Usage: git todo [-e] [-d] [-u] [-r] [-f] [-a \"new task to be appended\"] [branch]
 Options:
  -e Edit TODO list (through editor)
  -a Quickly append given task to TODO list (without opening editor)
  -u Undo last edit
  -r Undo last undo
  -d Delete TODO list
  -f Delete current TODO list and create a fresh one"
}

while getopts heurdfa: opt; do
  case "${opt}" in
    h) usage; exit;;
    e) mode="edit" ;;
    d) mode="delete" ;;
    u) mode="undo" ;;
    r) mode="redo" ;;
    f) mode="freshen" ;;
    a) mode="${mode:-edit}"; task="${OPTARG}";;
    *) exit 1;;
  esac
done
mode="${mode:-show}"

git_dir=$(git rev-parse --absolute-git-dir) || exit 1
todo_dir="${git_dir}/todo" ; mkdir -p "${todo_dir}"
branch="${!OPTIND:-"$(git branch --show-current)"}"
(git branch -a | grep -q "${branch}") || { echo "Given branch doesn't exist" >&2; exit 1;}
todo_file="${todo_dir}/${branch}"
[[ -e "${todo_file}" ]] || mode="edit"
header="### This is the TODO list for branch \"${branch}\". Write your tasks below. Separate tasks with blank line(s). ###"

show(){
  case "$(head -n1 "${todo_file}")" in
    "${header}") local read_from=2;;
    *) local read_from=1;;
  esac
  tail -q -n "+${read_from}" "${todo_file}" | cat -sb | fold -sw "$((COLUMNS-2))"
  echo
}

edit(){
  local editor=$(git config core.editor)
  [[ -e "${todo_file}" ]] || echo "${header}" > "${todo_file}"
  cp -n "${todo_file}" "${todo_file}.undo.candidate"
  if [[ -v task ]]; then
    echo -e "\n${task}" >> "${todo_file}"
  else
    "${editor:=vi}" "${todo_file}"
  fi
  if diff -q "${todo_file}" "${todo_file}.undo.candidate" &>/dev/null; then
    rm "${todo_file}.undo.candidate"
  else
    mv "${todo_file}.undo.candidate" "${todo_file}.undo"
    # Remove trailing blank lines. We use awk which can't do in place edit. So,
    # using the redo file which would have to be deleted anyway.
    awk '/^$/ {nlstack=nlstack "\n";next;} {printf "%s",nlstack; nlstack=""; print;}' "${todo_file}" > "${todo_file}.redo"
    # Ref: https://unix.stackexchange.com/a/81688
    # Credit: @HaukeLaging https://unix.stackexchange.com/users/32191/hauke-laging
    mv "${todo_file}.redo" "${todo_file}"
  fi
}

undo(){
  if [[ -e "${todo_file}.undo" ]]; then
    mv "${todo_file}" "${todo_file}.redo"
    mv "${todo_file}.undo" "${todo_file}"
  else
    echo "Nothing to undo" >&2
    return 1
  fi
}

redo(){
  if [[ -e "${todo_file}.redo" ]]; then
    mv "${todo_file}" "${todo_file}.undo"
    mv "${todo_file}.redo" "${todo_file}"
  else
    echo "Nothing to redo" >&2
    return 1
  fi
}

delete(){
  mv "${todo_file}" "${todo_file}.undo"
  cp "${todo_file}.undo" "${todo_file}.undo.candidate"
}

freshen(){
  delete
  edit
}

"${mode}"
exit