Compose: Add support for specifying custom dockerignore

[langri-sha]

I have a repository with several projects inside. Sometimes there's some code sharing and I have to set up the context to be a common root. Troubles arise when there are several images that use the same context, but require different sets of files.

This takes away the simplicity of maintaining a small context and using a straightforward COPY to preserve structure. What would really help is if I could specify something akin to:

x-foo: &foo
  build:
     context: .
     dockerfile: ./foo/Dockerfile
     dockerignore: ./foo/.dockerignore
x-bar: &bar
  build:
     context: .
     dockerfile: ./bar/Dockerfile
     dockerignore: ./bar/.dockerignore

[shin-]

My first intuition is that this is straying too far from the intended purpose of .dockerignore to really be desirable. Additionally, this is not supported by the Docker Engine and could lead to unexpected issues even if handled properly client-side.

Finally, I'm wary of condoning usage that involves arcane file whitelisting/blacklisting interactions. This is the wrong solution to your issue, IMO.

[thaJeztah]

Related topics/discussions in moby/moby;

• https://github.com/moby/moby/issues/12886 Add support for specifying .dockerignore file with -i/--ignore
• https://github.com/moby/moby/issues/37129 Proposal: add support for multiple (named) build-contexts

[sweetpalma]

I second this. Maintaining microservice monorepo may be very tiring sometimes - especially when you have to maintain dozens of almost identical .dockerignore files.

[dm17]

I don't quite follow... Is it not standard practice to have a docker-compose.yml with services that each have their own context & Dockerfile? And then have a unique .dockerignore file in each directory that has a Dockerfile?

[guillaume86]

@dm17 AFAIK it doesn't work if you need the context to be the root folder (or simply the same folder for 2 different services with different ignores).

It seems DOCKER_BUILDKIT supports the Dockerfile.dockerignore convention, but it is not available on windows hosts so not helpful in my case.