By default, the Packagist repository is the only registered repository in Composer. We can add more repositories to our Magento project by declaring them in composer.json. This way we get to register our own git repository as a source of packages, as follows:

composer config repositories.magelicious-royal-trek git [email protected]:foggyline/Magelicious_RoyalTrek.git

This command results in the modified composer.json file, with the repositories key amended as follows:

"repositories": {
    "0": {
        "type": "composer",
        "url": "https://repo.magento.com/"
    },
    "magelicious-royal-trek": {
        "type": "git",
        "url": "[email protected]:foggyline/Magelicious_RoyalTrek.git"
    }
},

We can see our magelicious-royal-trek entry added in there...