You ask for "but I'm looking for specific examples of setups/workflows that people use to keep a version history of edited files on a WordPress site" but you also mention products :)
You get above as answer a list of tools and some best practices but I will focus here on the workflows: THEY ARE NOT WORDPRESS SPECIFIC:
But for the general examples/setups/workflows:
For starters: there ARE CM patterns, so independent of tooling. Google on CM Patterns, a lot of books out there, wiki's even communities e.g. http://www.cmcrossroads.com/forums.
There are also guides on setting up a valid stream strategy (google stream strategy), etc...
I don't think there is anything special about WordPress deployments compared to CM Management incl distributed parallel development on large Siebel, SAP, Informatica, Java etc.. factories. It's really almost default.
What is missing, I think, is that noone has writing a CMplan for WordPress development (yet) (IEEE). Once someone has done that (tool independent). The requirements can be filled in, I think, with any tool.
I think the reason that plan has not been written is that almost all WordPress implementations are still done by 1 person with a simple development-production setup so not with multiple developers/designers in the build phase having to deploy different versions that are running in the test environment, for instance.
the CMP plan starts with identifying all CI's in other words: make a list of all types of CI's present in a WordPress implementation including the apps, plugins, database, documentation, help, content, config files, release notes (!), etc...). That is a good start. Then decide which ones you want to bring under CM.
Next decide on what causes changes on these CI's e.g. a customer call for a bugfix, or an upgrade that is needed. If done right, this leads to a situation where you have the feeling things are under control.
Decisions like merging back from production to development and the way to handle that is part of that chapter (2 main patterns here) (though ofcourse you should try to minimize these hotfixes).
Only later look for a tool to do CM on one side (which includes version management as one of the tools) and change management tooling on the other side (which keeps you sane).
I think that is the best workflow to start with since, as far as I googled, noone has done yet. I think once the first person has written a WordPress CM Plan (according to IEEE) every other WordPress person in the world can copy that plan and make adjustments and implement the patterns in their tooling.
Isn't that too much work/too heavy : depends if you have a company or not: it can save your ass big time one day to have good CM plan.