According to this link, it is possible to conntect to the corporate Git from SAP Web IDE:
https://help.hana.ondemand.com/webide/frameset.htm?b8427ec16ae64347b97d2d46fb28f7cd.html
I set up Git, enabled access over HTTPS, installed SAP Cloud Connector, configured Cloud to On-Premise tunnel, configured available resources, connected to the SAP Cloud Platform, created and configured the destination for the on-premise Git, enabled "Corp. Git Link for SAP Web IDE" service, checked connectivity on every step and everything is fine.
But what shall I enter in the URL text box when cloning repositories in SAP Web IDE?