I have two different versions of git. In the 1.6.2 version, git push does not have the -u option. It only appears in the 1.7.x version.
From the docs, the -u is related to the variable
branch.<name>.merge in git config. This variable is described below:
Defines, together with branch.<name>.remote, the upstream branch for the given branch. It tells git fetch/git pull which branch to merge. What is an upstream branch ?
"Upstream" would refer to the main repo that other people will be pulling from, e.g. your GitHub repo. The -u option automatically sets that upstream for you, linking your repo to a central one. That way, in the future, Git "knows" where you want to push to and where you want to pull from, so you can use git pull or git push without arguments. A little bit down, this article explains and demonstrates this concept.
This is no longer up-to-date!
Push.default is unset; its implicit value has changed in Git 2.0 from 'matching' to 'simple'. To squelch this message and maintain the traditional behavior, use: git config --global push.default matching To squelch this message and adopt the new behavior now, use: git config --global push.default simple When push.default is set to 'matching', git will push local branches to the remote branches that already exist with the same name. Since Git 2.0, Git defaults to the more conservative 'simple' behavior, which only pushes the current branch to the corresponding remote branch that 'git pull' uses to update the current branch.