A simple shell script for validating prettier has been used on the files that were changed according to git

git-prettier.sh

command -v prettier >/dev/null 2>&1 || { npm install -g prettier; }

usage() {
  echo "usage: git-prettier.sh (format|validate) [<commit>]"
}

must_provide_commit_error () {
  echo "Must provide a known revision to compare against"
  usage
  exit 1
}

must_provide_command_error () {
  echo "Must provide either 'format' or 'validate' as a command"
  usage
  exit 1
}

if [[ "$1" != "validate" && "$1" != "format" ]]
  then
    must_provide_command_error
fi

commit_hash=$(git log --pretty=format:'%h' -n 1 $2 2>&1)

if [[ $commit_hash == *"unknown revision"* ]]
  then
    must_provide_commit_error
fi

git diff --name-only $2 | grep \.js$ | xargs prettier --single-quote --trailing-comma es5 --write "$1"

if [[ $1 == "validate" ]]
  then
    changed_files = $(git diff --name-only | grep "\.js$")
    changed_filecount=$(echo $changed_filecount | wc -l)

    if (( changed_filecount > 0 )); then
      echo "You have changes, but they aren't prettier.
usage: git-prettier.sh $1

Files that are not prettier:"
      echo changed_files
      exit 1
    fi

    echo "Your changes are prettier."

fi