pre-commit-hadolint

#!/usr/bin/env bash

set -euo pipefail

HADOLINT_PREFIX_URL="https://github.com/hadolint/hadolint/releases/download"
HADOLINT_VERSION="v2.1.0"
OS=$(uname -s)
ARCH=$(uname -m)
HADOLINT_BINARY="hadolint-${OS}-${ARCH}"
HADOLINT_URL="${HADOLINT_PREFIX_URL}/${HADOLINT_VERSION}/${HADOLINT_BINARY}"

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
LOCAL_BINARY="${DIR}/${HADOLINT_BINARY}-${HADOLINT_VERSION}"

function mylock() {
    # *sigh*
    # macOS does not have flock so fall back to perl(!) if it's not
    # available
    if command -v flock &>/dev/null; then
        flock -x 200
    else
        perl -e 'use Fcntl qw(:flock); open($fh, "<&=", 200) || die "Cannot open"; flock($fh, LOCK_EX) || die "Cannot lock"'
    fi
}

# Download the binary if it doesn't already exist
# use the locking pattern from https://linux.die.net/man/1/flock
(
    mylock
    if [[ ! -x ${LOCAL_BINARY} ]]; then
        curl -o "${LOCAL_BINARY}" -L -sSf "${HADOLINT_URL}"
        chmod 755 "${LOCAL_BINARY}"
    fi
) 200> "${LOCAL_BINARY}.lock"

files=()

# only run hadolint if it looks like a Dockerfile
for f in "$@"; do
    case $f in
        (Dockerfile*|*/Dockerfile*)
            files+=( "${f}" )
            ;;
    esac
done

if [[ "${#files[@]}" -gt 0 ]]; then
    exec "${LOCAL_BINARY}" "${files[@]}"
fi

# if no files, exit successfully
exit 0