feat(build): make --output=tar,dest=- work + print error on build flag --output=type=INVALID

[iTrooz]

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Does this PR introduce a user-facing change?

make build flag `--output=tar,dest=-` have correct behaviour (streaming to stdout)
print error on build flag `--output=type=INVALID` instead of outputting image to folder `type=INVALID`

Note

I don't believe documentation changes are needed. I may be wrong ?

This PR lays the groundwork for introducing type=registry, which I will work on when this PR is merged

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[iTrooz]

I assume this change should be submitted against https://github.com/containers/buildah instead. But where am I supposed to put tests ? Should they stay in this repository ?

[Luap99]

I assume this change should be submitted against https://github.com/containers/buildah instead. But where am I supposed to put tests ? Should they stay in this repository ?

https://github.com/containers/buildah/blob/main/tests/bud.bats for example. Givent he same build command is eposed in buildah you should be able to to just add tests there. Once that is merged in buildah and we updated buildah here we can still have like one or two cases to validate that podman produces the same expected errors.

[mheon]

For when you port this over to buildah: I wonder if a check that /dev/stdout is not a TTY is appropriate? Streaming a tar file to the terminal isn't very useful, so we want to make sure the user is redirecting to a file or piping to another process.

[iTrooz]

Done ! containers/buildah#6476

I wonder if a check that /dev/stdout is not a TTY is appropriate?

Probably, especially since docker does it. I could submit this in a separate PR, but I'd like to keep this one focused on this