Development on SAP ERP is server based (i.e. all the source code is on the server, edited on the server and compiled just in time). The SAP Transport Management System is part of SAP's server-based software logistics and aims at:
- registering any change to the code or the database structure ("workbench orders") or to the software configuration ("customizing orders" which logs change to database tables marked as relevant for the software deployment)
- approving these changes (i.e. committing these changes and exporting them).
- deploying these changes following well defined transport routes (i.e. copying them to other environments, importing the changes and activating them, including upload of deployable data, database changes, etc...).
Source code versions are tightly intertwined with the TMS: its "transport orders" are the starting point for version management. But it's all very flat without branching. The branches are implicit: it's the system/environment on which you are developing; if you start a new change in development, this will be your development branch. Not so practical if you have to make an emergency patch on your production system.
For a software developer, it would be much more convenient to use GIT to manage ABAP code to benefit of advanced branching capability, instead of the old TMS. But since TMS is a core component that does a lot more than just source code management, you can't get rid of it on SAP ERP.
There's fortunately some light at the end of the tunnel:
It seems that someone developed ABAPGIT, a git client for ABAP development, that could bring in some GIT features. It's not a TMS replacement but rather a complement. Developments would nevertheless continue to take place on the server with one active version (no local repository on the developer's desktop).
With the newer product line SAP HANA, SAP seems to go further in this direction, offering a web IDE fully integrated with GIT for source code management.