Within one git repo, I have two separate applications (web server and API server).
How can I deploy each application to its own Heroku app?
(So there
When you have to separate application then you can simply push repository sub-tree to each.
Setup remotes once
heroku git:remote --remote heroku-client -a client-app
heroku git:remote --remote heroku-server -a server-app
And then you can deploy through pushing sub-tree to the remote
git subtree push --prefix client heroku-client master
git subtree push --prefix server heroku-server master
(where --prefix points to app's root folder)