Hello Luis,
Many thanks for your answer.
You are right, we can use the ABAP repository (that is the resulting BSP application) to control the version of the applications.
Actually once the SAP Fiori application has been deployed to an ABAP repository the first time, developers can change the application easily in the SAP WEB IDE by importing it.
However with this approach, there is not any tool supporting the collaborative development.
Imagine that two or more developers will change the same application simultaneously using the SAP WEB IDE.
If it is not possible to create a GIT repository for this application, they will not have any tool assisting them during the development: e.g. consolidating versions, resolving merge conflicts etc.
Regards.