Expose 'testingfarm.cli_args' as CLI option

[lukaszachy]

I use recipes which contain

fixtures:
  testingfarm:
    cli_args: "--repository-file URL"

Would be nice to be able to set this option via CLI (during schedule or execute) to avoid modifying the 'recipe' file.

[kkaarreell]

I am thinking if we should allow to specify any fixtures override from CLI. Nothing perfect, just add the respective option to the "fixtures" list, overriding an existing value.

newa schedule --fixture testingfarm.cli_args = "foo" ...

[lukaszachy]

I am thinking if we should allow to specify any fixtures override from CLI.

It will be more generic and cover my usecase as well, so +1

[kkaarreell]

As a workaround, you can define cli_args: "${TF_CLI_ARGS}" and define this variable on a cmdline.

[kkaarreell]

POC in #145