Gitlab supports Oauth applications to be authorized. Isnt it only authorization and not install? If it is install how can we install Deepsource to GitLab? I assume Gitlab doesn’t have a marketplace
Hey! 
Yes, we use GitLab oAuth applications for our integration. You’re technically correct in that there’s no “installation” as such. We handle that implicitly once you authorize your personal GitLab account with DeepSource. You can follow the steps detailed in the docs here.
I hope this helps!