This seems to assume that everyone is committing into the same branch. How about the workflow where you create a new branch for each work package and merge it into the main branch when finished? It lets you check in to your own branch as often as you want (even broken code) without worrying about breaking anything for the other devs. The merges will be bigger though, days or weeks of work. A good point is that the branch merge is a natural time to look through all the diffs.