Create local branches with remote tracking

[jansol]

When typing a new branch name in the branch switcher it offers to create a new branch by that name. However the Git CLI also automatically sets newly created braches up to track a remote if a remote branch with the same name exists and is unique. Zed could go a step further and provide a list of all known remote branches with the same name so users can choose which one to track.

Going further it would be nice to have the ability to specify a tracked remote with a completely different name, too. E.g. "upstream" for the main branch of the upstream repo.

[bersace]

I suggest to reuse current branch upstream if any.
I mean, one almost always create branch from origin/master.

What about a setting such as:

{
  "git": {
    "default_upstream": "same" // current, same, ask
  }
}

Just like now, the future upstream is printed in creation dialog.

This way, you can easily create a new PR from another, starting fresh from master.