Unwanted stack setting

[namoscato]

Thanks for the work on this GitHub Action!

Is there a reason for this line:

https://github.com/ElayGelbart/Heroku-Auto-Deployment/blob/714f7d7da9749f34ce2771c8ea1d665c9130509c/src/git/utils.ts#L13

This will actually upgrade applications on an older stack, which seems outside the scope of this GitHub Action.

[bstillwagon-mylo]

this is also downgrading the stack in other instances now as well. Would love for this to be a required env var passed in.