Revisit the upload subcommand? #222
Description
Looking over #218 made me realize that we'll likely be growing a very large amount of options on the upload subcommand, all of which are (currently) propagated to the build command.
There's also a problem that a two-step approach loses information about the produced image and thus the user has to manually specify a bunch of things such as the boot mode (UEFI, BIOS) and architecture. We could stuff all of this into some sort of metadata file (something close to describe?) but then users have to keep the two files together joined at the hip.
I don't have good answers for any of this but let's give it some thought. The workflow of build+upload in a single step feels well, the separate upload less so even though I'd much prefer them to always be two separate steps.