Add 'buildfile' option

[ohord]

As new version of docker supports -f option (specifying another than Dockerfile filename for configuration moby/moby#9707) it's reasonable to add this support in fig too. For example:

build: .
buildfile: mydocker.file

[coding2012]

Would be nice! 👍

[seven1m]

👍

We have an app that uses Dockerfile for production deployment, so I cannot use Fig for development, since it's impossible to point to another build file.

[dnephin]

I think it would be nicer to just keep this as build

build: ./mydocker.file

I suspect once that support is added to docker-py, fig should just work.

[dnephin]

@seven1m you should aim for a way to make the image work in any environment. You can probably extract any differences to be data volumes, or environment settings.

[dronov]

@dnephin yeah, I think that it would be correctly too.

[seven1m]

Thanks for the feedback. I'll investigate that some more, but seems easier said than done.

[cpuguy83]

@dnephin But there is the build file and then the build context.
For instance: docker build -f path/to/Dockerfile -t my_image ., where . is saying to use the current directory as the build context, and "-f" is pointing to a subpath of .. If only the Dockerfile is specified, then there would be no context uploaded, just the Dockerfile.

[dnephin]

Oh, I didn't realize they were also being decoupled. I thought the same rules applied but you could name the file within the root of the context. In that case another field works. Thanks @cpuguy83

[thaJeztah]

Yes, they are decoupled, with the restriction that the Dockerfile must be within the build context;

docker build -f $(pwd)/sub/sub/Dockerfile $(pwd)/sub/

Is allowed, but

docker build -f $(pwd)/sub/Dockerfile $(pwd)/sub/sub/

Is not, because the Dockerfile is outside of /sub/sub/

(Hope I wrote the examples correctly, the feature can be quite confusing LOL)

[coding2012]

Any chance we can make it so the Dockerfile does not have to be inside the build context? (though... I wonder if that would require a change to Docker rather than fig).

[majormoses]

@coding2012 pretty sure that you tar up the dir to send to docker to build therefore it cant be out of the build context. This is for security and I know has been discussed at great length on the docker end.