docker - How to specify different .dockerignore files for different builds in the same project?

Question

I used to list the tests directory in .dockerignore so that it wouldn't get included in the image, which I used to run a web service.

Now I'm trying to use Docker to run my unit tests, and in this case I want the tests directory included.

I've checked docker build -h and found no option related.

How can I do this?

Answer 1

Docker 19.03 shipped a solution for this.

The Docker client tries to load <dockerfile-name>.dockerignore first and then falls back to .dockerignore if it can't be found. So docker build -f Dockerfile.foo . first tries to load Dockerfile.foo.dockerignore.

Setting the DOCKER_BUILDKIT=1 environment variable is currently required to use this feature. This flag can be used with docker compose since 1.25.0-rc3 by also specifying COMPOSE_DOCKER_CLI_BUILD=1.

See also:

• https://github.com/moby/moby/issues/12886#issuecomment-480575928
• https://github.com/moby/moby/issues/12886#issuecomment-518843764
• https://github.com/moby/moby/issues/12886#issuecomment-523706042