pre-commit.sh

#!/usr/bin/env sh
#
# Executes on git commits. Unrelated to the other Bash scripts.
# https://codeinthehole.com/tips/tips-for-using-a-git-pre-commit-hook/
# https://gist.github.com/glfmn/0c5e9e2b41b48007ed3497d11e3dbbfa
#
# Requirements: prettier, shellcheck. Note shfmt is also run in the editor on
# saves.

# Colors
RED='\033[1;31m'
GREEN='\033[1;32m'
YELLOW='\033[1;33m'
NC='\033[0m'
BOLD='\033[1m'

# Git metadata
BRANCH_NAME=$(git branch | grep '.*' | sed 's/* //')
STASH_NAME="pre-commit-$(date +%s) on ${BRANCH_NAME}"
FILES=$(git diff --cached --name-only --diff-filter=ACMR | sed 's| |\\ |g')
[ -z "$FILES" ] && exit 0

echo "* ${BOLD}Checking for unstashed changes:${NC}"
stash=0
# Check to make sure commit isn't empty.
if git diff-index --cached --quiet HEAD --; then
  # It was empty, exit with status 0 to let git handle it.
  exit 0
else
  # Stash changes that aren't added to the staging index so we test only the
  # changes to be committed.
  old_stash=$(git rev-parse -q --verify refs/stash)
  git stash push -q --keep-index -m "$STASH_NAME"
  new_stash=$(git rev-parse -q --verify refs/stash)

  echo "  - Stashed changes as: ${BOLD}${STASH_NAME}${NC}"
  if [ "$old_stash" = "$new_stash" ]; then
    echo "  - no changes, ${YELLOW}skipping tests${NC}"
    exit 0
  else
    stash=1
  fi
fi

echo "* ${BOLD}Testing and formatting:${NC}"

# If using mulitple commands, append && to all but the last so if any one fails
# it's accurately represented in the exit code.
echo "$FILES" | xargs prettier --ignore-unknown --write &&
  echo "$FILES" | xargs git add &&
  shellcheck --check-sourced ./*.sh

# Capture exit code from tests
status=$?

# Inform user of failure.
echo "* ${BOLD}Build status:${NC}"
if [ "$status" -ne "0" ]; then
  echo "  - ${RED}failed:${NC} if you still want to commit use ${BOLD}'--no-verify'${NC}"
else
  echo "  - ${GREEN}passed${NC}"
fi

# Revert stash if changes were stashed to restore working directory files.
if [ "$stash" -eq 1 ]; then
  echo "* ${BOLD}Restoring working tree${NC}"
  if git reset --hard -q &&
    git stash apply --index -q &&
    git stash drop -q; then
    echo "  - ${GREEN}restored${NC} ${STASH_NAME}"
  else
    echo "  - ${RED}unable to revert stash command${NC}"
  fi
fi

# Exit with exit code from tests, so if they fail, prevent commit.
exit $status