Allow loading of values from .env file repo root

[jongio]

Some projects are going to want to put env vars that are shared in all envs and shipped in the repo, even as a placeholder, like this:

SOMEVALUE=

Right now we don't allow this because the user has to first create an env, then open the .env file, then copy and paste the values there.

I would like our code that loads env vars from the current env to also check and load a .env file from the root of the repo, if it exists.

Values in env/.env values would override values in root/.env, so load root/.env first and then env/.env

If we have .env file in root of repo

SOMEVALUE=FOO

And this in the env/.env file

SOMEVALUE=BAR

Then SOMEVALUE would be set to BAR

If we only have, root/.env:

SOMEVALUE=FOO

Then SOMEVALUE would be set to FOO.

[ellismg]

Spoke with @jongio and we are going change this slightly to say "a .env file next to azure.yaml" instead of "the root of a repo" but otherwise this makes sense. I have a small refactoring already of Environment as part of the ACA PR. We can do this next.

[savannahostrowski]

@ellismg @rajeshkamal5050 I think that supporting something like this would alleviate some of the headaches we're seeing around azd + environment variables (notably things like passing API keys down into Bicep). If we can load the .env in the root then a workflow like this:

1. Add API keys to the .azure/env name/.env
2. Define them in main.parameters.json
3. Define them as params at the top of main.bicep
4. Pass them into the container app module for my API
5. Define them at the top of api.bicep
6. Use them as env variables in the container app

could end up looking more like this with the simplified init flow:

1. Add API keys to the .azure/env name/.env
2. Defining them in main.parameters.json
3. Defining them as params at the top of main.bicep