The big change here is to pass around an explicit `*BuildOptions` object
as part of Compose operations like `up` & `run` that may or may not do
builds. If the options object is `nil`, no builds whatsoever will be
attempted.
Motivation is to allow for partial rebuilds in the context of an `up`
for watch. This was broken and tricky to accomplish because various parts
of the Compose APIs mutate the `*Project` for convenience in ways that
make it unusable afterwards. (For example, it might set `service.Build = nil`
because it's not going to build that service right _then_. But we might
still want to build it later!)
NOTE: This commit does not actually touch the watch logic. This is all
in preparation to make it possible.
As part of this, a bunch of code moved around and I eliminated a bunch
of partially redundant logic, mostly around multi-platform. Several
edge cases have been addressed as part of this:
* `DOCKER_DEFAULT_PLATFORM` was _overriding_ explicitly set platforms
in some cases, this is no longer true, and it behaves like the Docker
CLI now
* It was possible for Compose to build an image for one platform and
then try to run it for a different platform (and fail)
* Errors are no longer returned if a local image exists but for the
wrong platform - the correct platform will be fetched/built (if
possible).
Because there's a LOT of subtlety and tricky logic here, I've also tried
to add an excessive amount of explanatory comments.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
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