--Thank you for your job posting--
I am going to build your lambda function with python. The Lambda function can be build in such a way that it is triggered when a new commit is pushed. In this case, it should take the code from the repo and upload it to the S3-bucket. In your case, lambda function would likely need to include its own standalone git client library. I would start work right now once you share more details about yourrepositories.
Best regards.
Yevhenii L