Domino and XPages currently fall behind in build process automation (build automatically option in Domino Designer is really not what build automation means). Since 9.0.1 brings technology preview of a headless designer, I'll try to create a proof of concept for an end to end automated build.
I've tried to do some parts of it individually in past, but now it might fit all together.
Path should be:
1. Edit application in NSF in Domino Designer / or / Edit source code using other tools
(1a) Run some local tests
2. Check-in source code into Git repository
3. Trigger checkout from repository automatically
4. Build NSF and move it to test server
5. Run test - some itegration test and some UI test using TestNG and Selenium
6. Get nice report that I didn't break anyting in step 1
It seems like a lot of work, but once you get such framework in place is should be quite easy to use for other projects. And also all modern frameworks are going in this direction, so it should be something to pursue too.