#!/bin/sh
# SPDX-License-Identifier: MIT
set -eu
export TZ=UTC LC_ALL=C
export GIT_CONFIG_NOSYSTEM=1 GIT_CONFIG_GLOBAL=/dev/null
export GIT_AUTHOR_NAME='Example Author'
export GIT_AUTHOR_EMAIL='author@example.invalid'
export GIT_COMMITTER_NAME='Example Author'
export GIT_COMMITTER_EMAIL='author@example.invalid'
export GIT_AUTHOR_DATE='2026-10-25T12:00:00+00:00'
export GIT_COMMITTER_DATE='2026-10-25T12:00:00+00:00'
test "$(git version)" = 'git version 2.56.0'

start_case() {
  mkdir "$1"
  cd "$1"
  git init -q --template= --initial-branch=main --object-format=sha1
  git config commit.gpgsign false
  git config core.autocrlf false
  printf 'base\n' > note.txt
  git add note.txt
  git commit -qm 'Base note'
  printf 'base\nsecond line\n' > note.txt
  git commit -qam 'Add second line'
}

start_case soft-example
before=$(git rev-parse HEAD)
git reset --soft HEAD~1
test "$(git rev-list --count HEAD)" = 1
test "$(git status --porcelain=v1)" = 'M  note.txt'
test "$(git show :note.txt)" = "$(cat note.txt)"
printf 'Soft reset: one commit; second line remains staged\n'
git status --short
git log -1 --format='%h %s'
git reset --soft "$before"
test -z "$(git status --porcelain=v1)"
printf 'Saved commit restored before any further edits\n'
cd ..

start_case mixed-example
git reset --mixed -q HEAD~1
test "$(git rev-list --count HEAD)" = 1
test "$(git status --porcelain=v1)" = ' M note.txt'
test "$(git show :note.txt)" = base
test "$(cat note.txt)" = "$(printf 'base\nsecond line')"
printf 'Mixed reset: one commit; second line remains unstaged\n'
git status --short
cd ..

start_case amend-example
old=$(git rev-parse HEAD)
printf 'extra note\n' > extra.txt
git add extra.txt
git commit --amend -qm 'Add second line and extra note'
test "$(git rev-list --count HEAD)" = 2
test "$(git rev-parse HEAD)" != "$old"
test "$(git show HEAD:extra.txt)" = 'extra note'
test -z "$(git status --porcelain=v1)"
printf 'Amend: replacement commit includes the staged extra file\n'
git log -1 --format='%h %s'