Add CLI support for bulk environment variables

[bketelsen]

Required information

• Distribution: debian
• Distribution version: bookworm
  • Incus version: 6.3 daily

Feature Request

I've really been enjoying the OCI container support in Incus. In the process of moving my self-hosting bits from docker-compose to incus one thing that I've noticed is how much more typing it is to add -c environment.MYVAR=myvalue to the command line. I'm proposing adding a command line flag to the init/create and launch subcommands that will read environment variables from a file in standard KEY=value format, one pair per line.

Example

Given a file called .env with values:

MYSQL_PASSWORD=youruncle
MYSQL_USER=bob

Incus command could look like this:

incus init docker:mysql:latest --env .env

The command logic would read the lines from the .env file and merge them into the configuration before init/create/launch.

If acceptable, I'm willing to make this change as a pull request.

Thanks for incus!

[bketelsen]

Flag name --env is of course up for debate, but it appears that --env is available.

[stgraber]

I think that's fine, though I'd go for the longer --environment-file, a bit more of a pain to type (though that's what shell completion is for :)) but also more descriptive of what it will do.