Format Terraform files on a pre-coomit hook

tf-format.sh

#!/bin/sh

# Apply Terraform formatting to any .tf files modified during
# git changes that are staged.
# Make sure that you have terraform <YOUR_TERRAFORM_VERSION> installed.
# You can use TFSwitch to manage different versions of Terraform at once
# See: https://tfswitch.warrensbox.com/Install/
REQUIRED_TF_VERSION="Terraform v0.12.31"

# Halt the script if any pipe operations fail
set +o pipefail

TERRAFORM_VERSION=$(terraform --version | grep -Ei "v[[:digit:]]{1,}\.[[:digit:]]{1,}\.[[:digit:]]{1,}")

if [[ $TERRAFORM_VERSION != $REQUIRED_TF_VERSION ]] ; then
  echo "You have an invalid version of Terraform: $TERRAFORM_VERSION"
  echo "Please install $REQUIRED_TF_VERSION"
  exit 1
fi

FMT_OUTPUT=$(git diff --name-only --staged | grep '\.tf$' | xargs -I{} terraform fmt -write=true {})

# The variable "$?" holds the latest pipe operation exit code
# which in this case came from `terraform fmt`
if [[ $? == 0 ]] ; then
  echo "Terraform formatting applied successfully."
  exit 0
else
  echo "Terraform formatting error with code $?: $FMT_OUTPUT"
  exit 1
fi