today I learned how to use your own fork in composer when the maintainers don't accept pull request.
First set the version you in the required section to "dev-master" , composer some how assumes you want to require the master branch.
Second add your fork as a repository to your craft/composer.json
{
"require": {
...
"nmaier95/shopify-product-fetcher": "dev-master",
...
},
"repositories": [
{
"type": "vcs",
"url": "https://github.com/toyflish/craft-shopify-product-fetcher"
}
]
Last update your bundle
composer update