Problem:
You want to run a docker image build on Google Cloud Build, but the client is trying to upload a huge context image to Google Cloud even though you have added all your large directories to your .dockerignore and the build works fine locally.
Solution:
Google Cloud Build ignores .dockerignore by design – the equivalent is called .gcloudignore.
You can copy the .dockerignore behaviour for gcloud by running
cp .dockerignore .gcloudignore