More predictable output names

[supakeen]

When building an image like so:

sudo podman run --privileged \                
   -v ./output:/output \
   ghcr.io/osbuild/image-builder-cli:latest \
   build \
   --distro fedora-41 \
   minimal-raw

I can predict part of the result path, currently it'll be output/$distro-$release-$imagetype-$arch however, the path parts that come after that are unpredictable as they are xz/disk.raw.xz.

Perhaps we can make them more predictable by outputting:

output/$distro-$release-$imagetype-$arch.raw.xz

instead?

[mvo5]

Thank you! There are some hard-coded pieces in the image library currently around filenames, it would be nice to be more flexible here, some discussion is here osbuild/images#1039 - another source of hardcoding is osbuild itself that always creates the pipeline dir as prefix (c.f. https://github.com/osbuild/osbuild/blob/v137/osbuild/main_cli.py#L57)

[supakeen]

Perhaps we can take this together with (an expanded) version of osbuild/osbuild#1930 so we know which files to expect where and then move them into friendlier paths?