It creates a tracking branch, and so git knows how far a branch is relative to a remote branch.
1,572 karma · joined May 31, 2011
Sometimes you can go too far in questioning everything to get any practical result.
"The command’s second form creates a new branch head named <branchname> which points to the current HEAD, or <start-point> if given."
So after a git branch command, the test branch still points to the same commit as HEAD.
You have to make an additional commit for them to diverge.