---

This section details on the original issue you should resolve

<issue_title>BuildKit caching arguments</issue_title>
<issue_description>### Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

I am trying to persist the npm cache for my JavaScript app across CI builds. The default image created by AddJavaScriptApp uses the internal BuildKit cache (RUN --mount=type=cache,target=/root/.npm). To be able to reuse the cache across pipeline runes, I'd like to use a different backend, e.g. a local directory on an Azure Pipelines build agent in combination with the Cache task.
In order to do that, I would need to add additional arguments (--cache-to and cache-from) to the docker buildx build call in the container runtime, but while there is an option for build arguments, I couldn't find a way to add arguments to the call itself (see DockerContainerRuntime for example).

Describe the solution you'd like

I'd like to either have a possibility to control these caching arguments directly, or a generic way to add additional arguments to the image building call.

Additional context

This is not only about build performance. We use Font Awesome which bills us for the bandwidth used during package loads.</issue_description>

<agent_instructions>Update the ContainerBuildOptions class to take an AdditionalArguments property that will be relied to the docker build call. Model this API as a list of strings and initialize it to a non-empty list. Add tests that validate that additional properties flow correctly to the ContainerRuntime implementation.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@captainsafia @Skleni Thanks for filing this issue!

Right now, our API for customizing the arguments that are passed to the build command is the ContainerBuildOptions which exposes a small surface area of what is fully-supported in the Docker CLI.

A thought here is to expose an AdditionalArguments property that would allow the user to provide arbitrary arguments that aren't supported by the existing properties on ContainerBuildOptions. That should allow you to set these additional arguments on the call using the existing APIs for customizing ContainerBuildOptions:

builder.AddProject("api", "../api.csproj")
  .WithContainerBuildOptions(ctx =>
  {
      ctx.AdditionalArguments.Add("--cache-from", "type=registry");
  });
```</body></comment_new>
</comments>