fix: validate --env is not passed with an empty string

[monteiro-renato]

Looks like the CLI accepts --env="", and the deployment seems to "work"; There were no error messages in the console at least.
Looking at the portal it doesn't seem like anything gets deployed however.

I am not exactly sure how I could dig deeper into what happens when the deployment code is actually running, but I guess adding this extra validation can't hurt.

[cjk7989]

Hi @monteiro-renato , thanks for the fix! The bug is real and worth addressing. A few concerns:

Validation fires too late

By the time this check runs (~line 258), line 190 has already printed:
Deploying to environment:

The validation should be moved to the top of the function alongside other input checks, before any logging or processing occurs.

Error message is slightly misleading

Users can specify any custom environment name, not just preview. Suggest:

"Use a named environment (e.g. 'preview') or omit the flag."

[monteiro-renato]

@cjk7989, thanks for the review!
I've moved it upwards, let me know if there is anything else you would like me to change.

[cjk7989]

Looks good to me, approved. Thank you again :)