DockerAlias should use dockerRepository and dockerUsername from Docker scope

[jjst]

When originally introduced in 885541e dockerTarget used dockerRepository and dockerUsername defined in the Docker scope.

Sometime in the process of dockerTarget being refactored and renamed to dockerTag and then dockerAlias, it was made to use the value from dockerRepository from the global scope instead of the docker scope. ie, defining

dockerRepository in Docker := "my-custom-repository"
dockerUsername in Docker := "john"

used to work, but now has no effect, as shown by looking up the value of dockerAlias:

sbt:test-docker> docker:dockerAlias
[info] DockerAlias(None,None,test-docker,Some(0.0.0-SNAPSHOT))

Instead one must define them globally

dockerRepository := "my-custom-repository"
dockerUsername := "john"

sbt:test-docker> docker:dockerAlias
[info] DockerAlias(Some(my-custom-repository/john,None,test-docker,Some(0.0.0-SNAPSHOT))

I believe this was unintentional, and there's a fair amount of code out there still using the Docker scope for dockerRepository. This change reverts back to using the Docker scope for dockerRepository and dockerUsername when determining the docker alias. This change should be backwards-compatible as defining dockerRepository or dockerUsername on the Global scope means it's also inherited by the Docker scope.

Tested locally by defining dockerRepository both with no scope and with the Docker scope in a build file and examining the value of docker:dockerAlias. Happy to add a scripted test if required.

[muuki88]

Thanks a lot for taking care of this 😍

Actually I'm not quite sure if this was unintentional or not. Usually we don't scope the settings/tasks that are already prefixed with the format name (e.g. dockerRepository).

Still this change doesn't render dockerRepository := Some("...") code invalid, so keeping old code in other repos running is a good thing to do.