• one pushes into a special "staging" branch (e.g. st-XXX)
• buildbot builds/tests it
• if all is ok, buildbot rebases (or merges, depending on the content) it on top of the main branch, builds/tests again, and pushes into main
• optionally, updates pushed MDEVs from "Building" to "Closed"
• sends the result (success or failure, and what exactly failed) to the developer

optimizations:

• if something is built/tested in the st-* branch, there is no need to do it again in the main branch.
• if there are two pushes into two separate st-* branches, may be it would make sense to rebase/merge them first and build/test them in one buildbot run, not in three (first, second, merge).