Arbitrary CLI arguments for external sources

appstreamfile v0.1.0 only supports local File System from the image builder.

appstreamfile.exe -source local -location C:/path/to/config

For a tool like this, we definitely need to support S3, HTTP and other external sources. As the external sources are limitless, I need a way to determine the arguments, so its easy to expand for future integrations.

I’m thinking that it is fine to have source specific arguments for s3, http and so on, this is easily possible as BackendSource can have its own implementation to fetch the config

appstreamfile -source s3 --bucket my-bucket --key path/config.yaml
appstreamfile -source http --url https://example.com/config.yaml
appstreamfile -source local --path C:/path/to/config

Any concrete type implementing BackendSource can have arbitrary arguments and any way of of fetching the config in GetConfig() implementation.

type BackendSource interface {
	GetConfig() c.Config
}