Composer: checkout gitlab repo

I took a while to findout how to clone a external gitlabrepository via composer in a project

if your repository is available via git + ssh you have to create a  ssh key 

follow this link to do so
https://help.github.com/articles/generating-ssh-keys/

at next you have to add your ssh key to ssh-agent
exec ssh-agent bash
ssh-add ~/.ssh/id_rsa


 
composer.json in the root of your project

{
"repositories": [
    {
        "type":"vcs",
        "url":"git@gitlab:root/testproject2.git"
    }
],
 "require": {
        "peter1/peter2": "dev-master"
    },
"target-dir":"test"
}


peter1/peter2 = name of the repository in composer.json of repo you want to clone
target-dir = name of the directory in local folder "vendor"


the project you want to clone via composer needs a composer.json too.

{
    "name": "peter1/peter2",
    "description": "My New Project",
    "authors": [
        {
            "name": "Peter Böthig",
            "email": "mail@mymail.com"
        }
    ]
}