I would like a chance to review the changes before having Visual Studio 2012 automerge my files.
Disable the "Attempt to automatically resolve conflicts when they are generated.
When Visual Studio 2012 is installed it defaults with this option set. If you uncheck this box Visual Studio behaves as it did in the 2010 version. You are presented the Conflict Resolution window with options to AutoMerge, Merge Changes In Merge Tool, Take Server Version or Keep Local Version.