I agree with Christoph completely. People developing Modelica code (or any kind of code, actually) should always use an RCS. I'm trying hard to educate my students and colleagues to this basic concept, when they start sending me zipped files with Modelica code, God forbid. Trying to hide the file structure from the GUI just makes the whole thing confusing and unnecessarily harder to grasp.
As a consequence, Modelica tools should make life as easy and intuitive as possible to them. And it shouldn't be and expensive add-on, it should be built-in by design.
Some competitor tools have never shined on this front, I'm afraid, and this has impacted the community for a long time. I wish I had a more "text-editor"-oriented Modelica tool back in 2005-2007, when I was actively contributing to the Modelica.Media library, and I had to use a text editor if I wanted my intended changes only to show up in the SVN diffs (just change that single line in package.mo, please...). I am still resorting to text editors to develop portable Modelica code, for the very same reason. OK, I could use Eclipse for that, buth then I'd lack the GUI when it makes sense to use it.
In general, commercial Modelica tools try to hide the Modelica details to various extents (up to and including not actually showing the Modelica code at all). I think OpenModelica's approach has to be more transparent, that is, more open and more Modelica oriented :)
Let's do this right this time, and let's try to avoid copying features of other tools that have not proven to be satisfactory for RCS-based code development.
OMusability group members, please give your opinion by adding a comment to this ticket.
