Using a Git Branch in composer

composer.json

"repositories": [
        {
            "type": "composer",
            "url": "https://repo.magento.com/"
        },
        {
            "type": "vcs",
            "url": "[email protected]:webshopapps/module-shipper.git"
        }
    ],
"require": {
        "magento/product-community-edition": "2.0.7",
        "composer/composer": "@alpha",
        "shipperhq/module-shipper": "dev-SHQ16-613",
    },

What's important is that the branch is prepending with dev e.g. branch SHQ16-613 becomes dev-SHQ16-613 in composer 

See http://www.lornajane.net/posts/2014/use-a-github-branch-as-a-composer-dependency for source

I use dev-master and then once downloaded it defaults to master. Then I can checkout and merge branches as normal.