pkg/compose: build with bake: drop support for buildx v0.16 and lower

[thaJeztah]

buildx v0.17 was released a Year ago, so any version this conditional code was accounting for would be versions before that; the latest of which being buildx v0.16.2 (July 2024).

Given that those versions are long EOL and no longer supported, we can probably remove the conditional code.

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[glours]

LGTM, I let @ndeloof check also

[ndeloof]

LGTM, but I wonder we could check version number and warn user running an obsolete release of buildx

[thaJeztah]

That's always gonna be tricky; that applies to all binaries (cli, compose itself, buildx, ... ); we can somewhat fix it in packaging and set a minimum version, https://github.com/docker/packaging/blob/66807ae5e8fbbed4dd498bfe2891c504b78cf38b/pkg/docker-cli/deb/control#L19

[ndeloof]

I had in mind Mac/Windows installation with some users relying on homebrew or manual installation, or maybe an older version was selected. We could just check by versions.GreaterThanOrEqualTo(buildx.Version, xxx) if some unsupported version is selected

[thaJeztah]

Yeah, it's a tricky one; it's good to shell out to buildx because the alternative wasn't great, but it also means that the buildx bake command-line now becomes a formal contract / API for compose.

I wonder if we should consider moving the options-struct-to-command-line-flags conversion to a utility package in buildx; that way changes made in the buildx command-line will stay in lock-step with the code to set those flags (e.g. if a flag is added / removed / renamed / changed, the buildx maintainers can make sure the code that compose uses to call buildx bake is updated as well and set the right version-switch.

Perhaps it would even be an idea to have a (hidden) flag that acccepts a JSON-struct with all the options - that would have a more structured way to pass options to buildx when invoked; i.e., something like

docker buildx bake --___bake_options='{"version":"v0.29.1", "progress": "rawjson", "provenance": true .....}'

• Some version in that struct could tell buildx bake what version was expected to be used by compose, which could allow buildx bake to adjust things where needed (or detect "unknown fields" and produce an error that a newer verrsion is needed).
• Some of those options could even be implicit (e.g. when using __bake_options, then always use rawjson)

@crazy-max any thoughts? Would something like that make sense to do? (i.e. a flag or subcommand to execute buildx programmatically?)