Particularly if there's been a big refactor of the directory layout. The easiest way to do that is move the code and merge it, along with all the fixups needed,

Particularly if there's been a big refactor of the directory layout. The easiest way to do that is move the code and merge it, along with all the fixups needed, as a giant delete & add operation, and git won't necessarily figure it out. With care, it's possible even to merge different git repos into a single repo while preserving history. But it takes care; it's not a pit of success.