Since you mentioned OpenMW I thought I should mention Daggerfall Unity. It’s an rewrite of Daggerfall using the Unity engine, also requiring the original files. The best thing about is that the developers have made it easily moddable and a very healthy modding community has sprung up for it, some of which really make the game feel like what the original developers were going for but had to deal with the technical limitations of the time.
I mainly program in Visual Studio so I use it’s integration for simple commits, diffs, and checkouts. Anything more complicated than that I head for the command line.