Git branches don't preserve loaded/unloaded project state in Visual Studio solutions

I'm surprised to find that the loade开发者_StackOverflow社区d/unloaded state of my Visual Studio (2008) projects is not maintained when I switch between git branches in which one should have all loaded and one should have some unloaded.

I thought this was maintained in the .sln file, which would be versioned in each branch, but that seems not to be the case (.sln is not in my .gitignore file).

Is this information stored someplace else, or is there some other reason that it might not be carrying over?

---

That information is saved as part of the megalithic binary "SUO" file.

How to test:

1. Open solution, mark project Unavailable
2. Close solution, open solution. Note still Unavailable
3. Close solution. Delete SUO. Open solution. Note project is Available.

(Also, that's the only file modified with changes :-)