Recently I started using gh for working with my forks. Before that I used to add the remotes manually.

When cloning a fork, gh adds the original repository as a upstream remote which is what I used to do manually, but if you try to find the branches, you’ll find that it only tracks the default one.

For tracking all of the branches in the upstream remote too, you just need to find the fetch line under the upstream section in the .git/config file.

For example, this is the content of my .git/config after cloning my go fork:

$ cat .git/config 
[core]
	repositoryformatversion = 0
	filemode = true
	bare = false
	logallrefupdates = true
[remote "origin"]
	url = git@github.com:alexsaezm/go.git
	fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
	remote = origin
	merge = refs/heads/master
[remote "upstream"]
	url = git@github.com:golang/go.git
	fetch = +refs/heads/master:refs/remotes/upstream/master

But what I really want under the upstream entry is this:

[remote "upstream"]
        url = git@github.com:golang/go.git
        fetch = +refs/heads/*:refs/remotes/upstream/*

After changing that file, you can do a git fetch --all :)