bake: initial implementation

[tonistiigi]

Initial implementation for #13 (formely buildfile)

Testing:

> make
cd compose
docker buildx bake
docker buildx bake -f config.hcl release
docker buildx bake -f config.hcl --set db.args.FOO=bar release
# see config.hcl for full data format
# --print shows the parameters that would be used by individual builds without invoking it

The compose part is pretty basic and should work as expected. The full internal datastructure for defining targets probably needs some design work and doesn't look right to me.

Alternative designs:

group "default" {
	targets = ["db", "webapp"]
}


target "%-cross" {
	platforms = [
		"linux/amd64",
		"linux/arm64"
	]
}

---
docker buildx bake default-cross

target "default" {
	targets = ["db", "webapp"]
}

target "default-cross" {
	targets = ["db", "webapp-cross"]
}

target "webapp" {
	context = "./"
	dockerfile = "Dockerfile.webapp"
	args = {
		buildno = "123"
	}
}

group "default" {
	targets = ["db", "webapp"]
}

group "default-cross" {
        inherits = ["cross"]
	targets = ["db", "webapp"]
}
target "cross" {
	platforms = [
		"linux/amd64",
		"linux/arm64"
	]
}

---
docker buildx bake default-cross

Outputs not supported yet, thinking if this should be per target or global.

@tiborvass @AkihiroSuda @seemethere @dmcgowan

[AkihiroSuda]

Looks good, but why HCL?

[tonistiigi]

@AkihiroSuda I don't really care about the format that much. Could accept anything that we can parse. You can use JSON as well (and thinking if we should allow json5). Examples use HCL cause I personally found it more readable and better than toml on comparisons. I'm not a big fan of yaml but the main thing is that I'd want to avoid something that looks like compose but isn't compose. Atm. bake accepts vanilla compose with no changes and I think we should keep it this way. If you want you can use compose with the override logic as well. If you as a user like yaml and compose already you can just keep using that and never care about the other formats.

[tonistiigi]

updated buildkit to bring in moby/buildkit#929

[tiborvass]

Are there compose files without .yml or .yaml suffixes? Why not error out?

[tonistiigi]

I have no idea. Does compose force you to use .yml suffix currently, I think not.

[tiborvass]

?

[tonistiigi]

The key does not exist atm. but should later.

[seemethere]

lgtm

[FernandoMiguel]

@tonistiigi what ever happened to --set db.args.FOO=bar ?

[tonistiigi]

@FernandoMiguel wdym?

[FernandoMiguel]

@FernandoMiguel wdym?

@tonistiigi in the OP example
docker buildx bake -f config.hcl --set db.args.FOO=bar release

I'm trying to pass args to my buildx