prettier pre-commit git hook

pre-commit

#!/bin/sh

set -e
exec 1>&2

warn(){
	printf '\x1b[31m%s\x1b[0m\n' "$*" >&2
}

projroot=.
emptyblob=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391

if ! test -e "$projroot/node_modules/.bin/prettier"
then
	warn "prettier npm module not found, skipping prettier"
	exit 0
fi

blacklist=/tmp/$$.blacklist
trap "rm -f '$blacklist'" EXIT
cat >"$blacklist" <<!
.eslintrc.js
!

check_files(){
	extension="$1"
	shift

	git diff-index --cached --name-only --diff-filter=ACM HEAD -- "$@" \
	| while read file
	do
		if grep -F "$(basename "$file")" "$blacklist" >/dev/null
		then
			echo >&2 "not prettifying '$file' - blacklisted"
			continue
		fi

		newblob=$(git show :"$file" \
			| (cd "$projroot" && node_modules/.bin/prettier --stdin-filepath "a.$extension") \
			| git hash-object -w --stdin)

		if test $(git rev-parse :"$file") != $newblob
		then
			if test $newblob = $emptyblob
			then
				# prettier gave us nothing - emitted an error
				echo "prettier error on $file" >&2
				exit 1
			fi
			warn "prettier changed \"$file\""
			git update-index --cacheinfo 100644 $newblob "$file"
		fi
	done
}

check_files js '*.js' '*.jsx'
check_files less '*.less'