> Do the same commits of A then have different parents depending on which branch they are on? Absolutely not. Commits are immutable (representing whole repo st

> Do the same commits of A then have different parents depending on which branch they are on? Absolutely not. Commits are immutable (representing whole repo state, not a diff), and branches are just (mutable) pointers to them. As the sibling already noted, a merge commit is just a regular commit. It simply points to multiple parents, "merging" them. Aside of the whole machinery to resolve conflicts etc. that's pretty much all there is to it. When your graph topology allows it, you can also merge branches without generating a new commit (so called "fast forward" merges) - such a merge does nothing but rewrites the branch pointer. You can also create merge commits that point to more parents than two ("octopus" merges). Reconciling the commits' content can get quite complicated in such cases, but from the repo graph perspective it's nothing special.