Feature request: flyctl launch --build-arg

The flyctl deploy command supports the --build-arg option but the flyctl launch command does not.

(I’m a little unclear on the difference between those two commands to be honest, but it does feel like it would be useful to be able to pass that option directly to flyctl launch, especially when providing getting started documentation for other people that want to deploy projects I have built).

@Simon_Willison I’d suggest putting this up directly as a feature request on Issues · superfly/flyctl · GitHub — we can discuss the actual code references there and you’ll get also notifications if and when changes have been merged.