[yuhc]

> At Meta we call an individual set of changes made to the codebase a “diff.”

This statement is definitely a misleading one. A diff itself is always a commit in the history log, and a diff can't be a group of multiple smaller units unless their team submit change set to git first and sync the squashed commit back to fbcode. But even in that case, from fbcode's view the squashed commit is still a diff.

A set of changes is called diff stack.