Passing environment variables to commands in the run section of a Bravefile currently has to be done using shell commands (sh -c 'TEST_VAR="test" ...'). Relying on the shell is not ideal and leans into an imperative style of programming, rather than the declarative style of the rest of the Bravefile.

The LXD client provides official support for passing environment variables to exec commands, which works reliably and with minimal changes to the code. A small extension to the Bravefile's command to include an "env" field that exposes this would allow for an easy, declarative way to pass env variables to commands that does not involve spinning up a shell process.

Additionally, being able to avoid the sh command tends to make the intent of the command clearer - see the example below.

Before:

run:
  - command: sh
    args:
      - -c
      - 'AUTH_ADDR=10.0.0.15:80 LOG_ADDR=10.0.0.25:8000 flask run'

After:

run:
  - command: flask
    args:
      - run
    env:
      AUTH_ADDR: 10.0.0.15:80
      LOG_ADDR: 10.0.0.25:8000