Just because you might find this interesting: Scion deviates significantly in this regard in order to deal with merges; coming from git, we land code to our main branch via merge so it's a common occurrence.
We do discourage (but not block) some trickier DAG things you could have done in git and are probably moving towards squashing and rebasing for landing since many things become simpler without merges, but we simply had to deal with merges (and handle git compatibility while migrating) to pull this off. Particularly, full DAG merge bases add a lot of complexity and it gave us some concrete ideas on how to improve git's commit graph data structures by an order of magnitude or more.
We do discourage (but not block) some trickier DAG things you could have done in git and are probably moving towards squashing and rebasing for landing since many things become simpler without merges, but we simply had to deal with merges (and handle git compatibility while migrating) to pull this off. Particularly, full DAG merge bases add a lot of complexity and it gave us some concrete ideas on how to improve git's commit graph data structures by an order of magnitude or more.