pre-commit

#!/usr/bin/env bash
# Usage: ln -sf ../../pre-commit .git/hooks

# Exit at first error
set -Eeu

# To handle partially committed files, we must copy the staged changes to a
# separate location
# See also https://stackoverflow.com/a/36793330
TEMPDIR=$(mktemp -d)
trap "rm -rf $TEMPDIR" EXIT SIGHUP SIGINT SIGQUIT SIGTERM
git checkout-index --prefix=$TEMPDIR/ -af

# keep using the same node_modules/ directory, not a new one in the temporary
# directory this avoids re-parsing everything from scratch every time we run
# the script
GIT_ROOT=$(git rev-parse --show-toplevel)

# prevent committing any file with a "NOCOMMIT" marker
if git diff --cached --diff-filter=AM -- ':!pre-commit' | grep -C3 'NOCOMMIT' --color; then
    echo "Commit contains NOCOMMIT markers. Aborting commit."
    exit 1
fi

# lint
if ! git diff --cached --name-only --diff-filter=AM --quiet -- src/lib.js; then
    if ! [ -e node_modules ]; then
        npm ci
    fi
    (cd $TEMPDIR; ln -sf $GIT_ROOT/node_modules node_modules; npm run lint)
fi