Xoogler here. There were tons of benefits to Google's approach, but they were only viable with crazy amounts of tooling (code search, our own version control sy

Xoogler here. There were tons of benefits to Google's approach, but they were only viable with crazy amounts of tooling (code search, our own version control system, the aforementioned CitC, distributed builds that reused intermediate build objects, our own BUILD language, specialized code review tools, etc). I'd say the major downside was that this approach basically required a 'work only in HEAD' model, since the tooling around branches was pretty subpar (more like the Perforce model, where branches are second-class citizens). You could deploy from a branch but they were basically just cut from HEAD immediately prior to a release. This approach works pretty well for backend services that can be pushed frequently and often, but is a bit of a mismatch for mobile apps, where you want to have more carefully controlled, manually tested releases given the turnaround time if you screw something up (especially since UI is really inefficient to write useful automated tests around). It's also hard to collaborate on long-term features within a shipping codebase, which hurts exploration and prototyping.