We went over this before. At some point (I think git 1.8.0) git requires you to be explicit about this and `git push t12345` doesn't work (I have explicitly tried it and it still causes the message).  Although in double checking this, I found: http://stackoverflow.com/questions/6089294/git-why-do-i-need-to-do-set-upstream-all-the-time which has some simpler ways of doing it, so I will update the documentation to reflect that.