"Do no harm" pre-commit template.

pre-commit

#!/usr/bin/env bash

# "Do no harm" autoformatter pre-commit script template.

# This example uses gofmt on all .go files.

# Files matching this pattern will be auto-formatted.
FILE_PATTERN='\.go$'
# The tool to check for.
FORMAT_TOOL=gofmt
# The format command. File names will be appended to this.
FORMAT_COMMAND=(gofmt -s -w)

# Find all staged files that meet some criteria, and exit early if there aren't any.
MATCHING_FILES=(`git diff --name-only --cached --diff-filter=AM | \
  grep --color=never "$FILE_PATTERN"`)
if [ ! "$MATCHING_FILES" ]; then
  exit 0
fi

# Verify that our formatter is installed; if not, warn and exit.
if [ -z $(which "$FORMAT_TOOL") ]; then
  echo "$FORMAT_TOOL not on path; can not format. Please install."
  exit 2
fi

# Check for unstaged changes to files in the index.
CHANGED_FILES=(`git diff --name-only ${MATCHING_FILES[@]}`)
if [ "$CHANGED_FILES" ]; then
  echo 'You have unstaged changes to some files in your commit; skipping '
  echo 'auto-format. Please stage, stash, or revert these changes. You may '
  echo 'find `git stash -k` helpful here.'
  echo
  echo 'Files with unstaged changes:'
  for file in ${CHANGED_FILES[@]}; do
    echo "  $file"
  done
  exit 1
fi
# Format all staged files, then exit with an error code if any have uncommitted
# changes.
echo 'Formatting staged files . . .'
${FORMAT_COMMAND[@]} ${MATCHING_FILES[@]}
CHANGED_FILES=(`git diff --name-only ${MATCHING_FILES[@]}`)
if [ "$CHANGED_FILES" ]; then
  echo 'Reformatted staged files. Please review and stage the changes.'
  echo
  echo 'Files updated:'
  for file in ${CHANGED_FILES[@]}; do
    echo "  $file"
  done
  exit 1
else
  exit 0
fi