git workflow for staging deployment with multiple feature branches (aka. easy branch replace)

Question

i'm looking for an easy way to make sure one local feature-branch completely 1:1 replaces a a remote deployment branch whereas the deployment branch is nothing else than a vehicle to deploy.

the setup

remote

master: deploys to production
stage: deploys to staging

local developer a

master -> remote master
feature A
feature B

local developer b

master -> remote master
feature C
feature D

the question

now let's say developer A wants to show his feature A to the boss. therefore he needs to deploy it on the staging server, to do so he merges his feature A into stage, and pushes and deploys. but what if now developer A wants to show feature B or developer B wants to show feature C or D. to make sure theres no interference it has to be guaranteed that only one feature is on the server and not two or three.

the only way i know of now is that the deployment branch stage is reverted until it resembles master and then another feature can be merged into it for deployment. or one could "simply" delete the branch stage and then recreate it from master.

so how can this be achieved easily? is this in fact a force push?

cheers!