There are a couple of options you can tweak for this scenario. Both are under the Documents Options
- Tools -> Options
- Environment -> Documents
The first option is to just uncheck “Detect when files changed outside the environment”. This will stop the reload dialog but will force you to manually reload.
The second option just below it is a bit better “Auto-load changes, if saved”. This will just automatically load the changes without prompting you for every project.
Personally though I would go a slightly different route here. The problem is occuring because your managing your source code control outside of Visual Studio. If you switched to using an addin to manage within Visual Studio it would remove these problems altogether. For svn there are several free packages available including Ankhsvn which is fairly popular