For msysgit 1.8.0, download git-credential-wincred.exe from https://github.com/downloads/msysgit/git/git-credential-wincred.zip and put into C:\Program Files\Git\libexec\git-core
For msysgit 1.8.1 and later, the exe is built-in.
in git config, add the following settings.
[credential] helper = wincred