Hi,
Whilst I'm not sure this is something we'd look at any time soon, I wonder if you could clarify the exact requirement (out of curiosity!)- the login to the SQL Server is handled via SSMS, so I'm guessing you mean a login to your VCS? In some cases (such as Visual Studio Online) we merely show the standard login dialog, so couldn't do much about it, but for others, such as SVN, we pop up our own username/password box and could potentially make changes. The vast majority of VCS clients will then cache your login credentials though, so you only have to log in once anyway.