Update local tracking refs when pushing- no way to disable

In this commit: b516968ff62ec153e008d033c153affd7ba9ddc6

I don't know if anyone else has the same way of working as I do, but I tend to set the "remote.<name>.skipDefaultUpdate" property to true for my publicly visible repository, just so I don't have duplicate branch heads lying around in my local repository. Call this peculiar, but I like it that way. However, git-push does not respect this property, meaning I know have these branches whether I want them or not. In a tool such as qgit or even 'git branch -a' output, it starts to get awful cluttered.

I'm not terribly familiar with GIT internals, so I don't know that I am the best to make a patch for this, but I'll take no response as a answer that I should start coding something up. Please CC me on emails, I'm not on the GIT mailing list.

-Dan