Run cmd if checksum changed

.gitignore

#...
.lets-checksums

lets.yaml

commands:
  maybe_run_npm_i:
    description: Runs npm i if needed
    checksum:
      - package.json
    cmd: |
      bash ./scripts/run-if-checksum-changed.sh maybe_run_npm_i $LETS_CHECKSUM "npm i"

run-if-checksum-changed.sh

#!/usr/bin/env bash

LABEL=$1
NEW_CHECKSUM=$2
CMD=$3
CHECKSUM_FILE_NAME=".lets-checksum"

function read_checksum() {
    if [[ ! -f "$CHECKSUM_FILE_NAME" ]]; then
    touch "$CHECKSUM_FILE_NAME";
    fi;
    PREV_CHECKSUM=$(grep -m 1 -E "^$1=\w+" "$CHECKSUM_FILE_NAME" | awk -F\= '{print $2}')
}

function update_checksum() {
    if [[ ! -f "$CHECKSUM_FILE_NAME" ]]; then
    touch "$CHECKSUM_FILE_NAME";
    fi;

    LINE_NUMBER=$(echo $(grep -m 1 -E "^$1=\w+" "$CHECKSUM_FILE_NAME" -n | cut -f1 -d:))
    if [[ -n "$LINE_NUMBER" ]]; then
        sed "${LINE_NUMBER}"'s/.*/'"$1"'='"$2"'/' "$CHECKSUM_FILE_NAME" > "$CHECKSUM_FILE_NAME"2 && mv "$CHECKSUM_FILE_NAME"2 "$CHECKSUM_FILE_NAME";
    else
        echo $1=$2 >> "$CHECKSUM_FILE_NAME";
    fi;
}

read_checksum "$LABEL"

if [[ "$NEW_CHECKSUM" != "$PREV_CHECKSUM" ]]; then
    update_checksum "$LABEL" "$NEW_CHECKSUM"
    eval $CMD
fi;