Add the ability to specify a custom branch name for a specific commit

[mkarajohn]

Right now, at my work, in order to not trigger CI/CD for every single PR of a stack, we only trigger review app deployments for PRs of branches that start with a specific prefix (e.g. review/).

SPR adds its own branch name, for every PR of the stack, breaking the aforementioned workflow (no review apps get deployed at all).

Would it be possible to add an option to specify the branch name of a certain commit from the stack?