I\'m trying to use composer to automatically clone a git repository from github that isn\'t in packagist but it\'s not working and I can\'t figure out what am I doing wrong.
Just tell composer to use source if available:
composer update --prefer-source
Or:
composer install --prefer-source
Then you will get packages as cloned repositories instead of extracted tarballs, so you can make some changes and commit them back. Of course, assuming you have write/push permissions to the repository and Composer knows about project's repository.
Disclaimer: I think I may answered a little bit different question, but this was what I was looking for when I found this question, so I hope it will be useful to others as well.
If Composer does not know, where the project's repository is, or the project does not have proper composer.json, situation is a bit more complicated, but others answered such scenarios already.