Pass compatibility flag to v2

[mat007]

Fixes #15

[ndeloof]

Too late, but a strong 👎 on this.
Many users (including me) use docker-compose as a command and expect a full V2 target. This should not just be considered a "legacy compatibility" mode

[mat007]

Ah sorry @ndeloof I should have pinged you when creating this PR.

Can you elaborate a bit? If you’re expecting V2, is there any reason you can’t directly invoke docker compose?

[ndeloof]

As of 2.0.1 compose v2 is distributed on a few Linux distros (typically: arch) as drop-in replacement for docker-compose
I also have a bunch of scripts here relying on docker-compose but still wanted to use V2.

IMHO compose v2 should not be restricted to "cli plugin" and docker space compose, this is just the new compose.

[mat007]

But isn’t docker-compose usable as a standalone binary now?
Discussing with @ulyssessouza he mentioned that Arch Linux are actually using the plugin directly as a binary just like that?

[ndeloof]

Yes indeed, our released binary can be used both as a CLI plugin or standalone binary as drop in replacement for docker-compose. That's my point: using the latter I expect I can run compose V2 I installed, I'm not in a hidden transition phase