ADD over curl documentation does not cover all cases

[adyanth]

Is this a docs issue?

• My issue is about the documentation content or website

Type of issue

Information is incorrect

Description

This PR #18582 changed the recommendation from using curl/wget to always using ADD. But it does not fully address the image size and layers increasing, only showing an example to that effect to mitigate it by ADDing to a scratch layer and bind mounting the required remote URL. It does not distinguish between the fact that the ADD runs on the host/buildkit v/s curl which would run in the environment setup by the Dockerfile (important for proxies and such). It does not acknowledge the caching behavior changes, accompanied by how ADD redownloads the file each time to check for changes (which might not be desirable in all situations).

Location

https://docs.docker.com/build/building/best-practices/#add-or-copy

Suggestion

Can send a PR to make the distinction between the ADD recomendation over curl clearer while noting the changes in behavior that result due to the change.