Quickly edit a file that was changed in the last git commit

git-fixup

#!/usr/bin/env bash

# SPDX-FileCopyrightText: 2020 Kirill Elagin <https://kir.elagin.me/>
# SPDX-License-Identifier: MPL-2.0

###
#
# Quickly edit a file that was changed in the last git commit.
#
# Sometimes you want to make a quick amendment to what you did in your last
# commit, but you already closed your editor. So you have to remember what
# file you edited, launch your editor, and type the file name again – it is
# somewhat cumbersome. Wouldn’t it be cool if you could just type:
#
# $ git fixup
#
# and have your editor launched with the file you edited in it? And if your
# last commit changed multiple files, you could choose which file to edit?
# This small script does exactly this.
#
# Use:
#
# * Download this script and put it somewhere on your $PATH.
# * $ git fixup
# * or $ git fixup <commit>
#
# Requirements:
#
# * git (obviously)
# * tput (probably comes with your distribution)
# * $EDITOR set to the editor you use
#
# https://gist.github.com/kirelagin/70abed1c291e42b198c9970bbe5368e5
###


changed=()

mode=''
while IFS= read -r -d '' line ; do
  if [ -z "$mode" ]; then
    mode="$line"
  else
    mode=''
    changed+=( "$line" )
  fi
done < <(git diff-tree --no-commit-id --name-status --diff-filter=AM -r -z "${@:-HEAD}")


chosen=''

if [ "${#changed[@]}" -lt 1 ]; then
  printf 'No files to edit!\n'
  exit 1
elif [ "${#changed[@]}" -eq 1 ]; then
  chosen="${changed[0]}"
fi

if [ -z "$chosen" ]; then
  i=1
  for file in "${changed[@]}"; do
    printf '[%d]\t%s\n' "$i" "$file"
    i=$((i + 1))
  done
  printf '\n'

  while [ -z "$chosen" ]; do
    read -r -p 'Choose a file to edit: ' c || exit 1
    if [ "$c" -ge 1 ] 2>/dev/null && [ "$c" -le "${#changed[@]}" ] 2>/dev/null; then
      chosen="${changed[$((c - 1))]}"
    else
      tput cuu 1
      printf 'Enter a number between %d and %d.\n' 1 "${#changed[@]}"
    fi
  done
fi

printf 'Editing `%s`\n' "$chosen"

# shellcheck disable=SC2086
exec $EDITOR "$chosen"