Multi-env warn of branch mismatch.

[jarrettj]

Is your feature request related to a problem? Please describe.
More of an inconvenience. Might just be me though. But I usually don't remember to amplify env checkout branch.

Describe the solution you'd like
If you are on a different branch to the env currently used by amplify, warn the user during an amplify push.

Describe alternatives you've considered
Updating my bash config to call both commands at once.

Additional context
N/A

[hisham]

+1. I ran into this as well and once ended up accidentally pushing prod client app pointing to non-prod resources. I just ended up hardcoding the prod appsync resources in my client app when a prod build is made.

[UnleashedMind]

Thanks for your feedbacks, we'll review it.