[expo-cli] consolidate env variables.

[jkhales]

This fixes #2280.

NB: in case of conflict we chose to prioritize the flag over the env variable.

Joint with @quinlanj

tests

• manually tested expo upload:ios with flags and env var

[jkhales]

Tests are failing but unrelated to our PR.

[cruzach]

thanks for taking care of this one 🙏
Since we were prioritizing the environment variable over the flag before, and now we're doing the opposite, this still might constitute a breaking change (although I do agree that if both are provided, it seems intuitive to fallback to whatever was provided by the flag).

We could keep the original behavior, but if you provide both and they aren't equal, we log an error? something like

You've provided contradictory Apple IDs. You should provide either [env var] or [flag], not both. Falling back to [whichever we fall back to].

unrelated- we'll need to update the docs as well

[jkhales]

You've provided contradictory Apple IDs. You should provide either [env var] or [flag], not both. Falling back to [whichever we fall back to].

Thanks for catching the missing docs, updated!
Warnings are a nice touch, added.

Regarding the breaking behavior, we had discussed this and think that this is the intuitive behavior and further this happens only when a user is doing multiple things wrong so we felt comfortable moving ahead with it.

[cruzach]

just one typo fix

this happens only when a user is doing multiple things wrong

I wouldn't say passing both the flag and the env variable is necessarily wrong, but if we are changing this then might as well add a changelog entry listing this as a bug fix so it's easily identifiable for that extremely rare case where someone maybe was relying on this behavior

[jkhales]

just one typo fix

this happens only when a user is doing multiple things wrong

I wouldn't say passing both the flag and the env variable is necessarily wrong, but if we are changing this then might as well add a changelog entry listing this as a bug fix so it's easily identifiable for that extremely rare case where someone maybe was relying on this behavior

b245cf5