Is there a way in TFS to edit files and then (maybe) merge them later without having to do a checkout? Basically edit then only touch source control when I decide to update to the server, not in advance.
Or has 5 years of Mercurial and Git just led to me getting confused about how TFS works and what I want is not possible and doesn't matter because "checkout" is not exclusive. (most likely option? :-) )
(I have been here but that does not solve my issue)
There are ways to cheat that, but there's no good reason to do so. When you check out code from TFS, you're getting a local copy to work with. When you check it back in, it creates a changeset, which is an atomic commit of your changes to the source code repository. If you don't want to check it in, and go off and do something else, you can create a shelveset, which can be named and unshelved whenever you're ready. Similarly, if you use Gated check-ins, that process creates a shelveset automatically and sends that for a validation build. If it fails, you just make changes to your shelveset and try again. If it succeeds, it checks a changeset into the source repository. It helps prevent checking in breaking changes.