I was getting the error:
An error occurred. Detailed message: An error was raised by libgit2. Category = FetchHead (MergeConflict).
3 conflicts prevent checkout.
To resolve this problem, I installed the 3rd-party Git command prompt tools, then you can open a Windows git command prompt from Visual Studio 2013: http://msdn.microsoft.com/en-us/library/vstudio/dd286572.aspx#commands
When I entered the command: git pull, I got the real error cause:
After removing these files and entering the commands:
git stash
git pull
The error was resolved.