The old commit becomes orphaned in your local workspace. The new, amended commit replaces the previous commit at the tip of the currently selected branch. As such, it is more accurate to say the git ...

Git uses your changes, the parent commit, and some metadata to build the new commit; the parent is required. Unless, that is, you explicitly tell it to create orphan branches.

Git is very flexible, but you do have to know the magic incantations. For example, suppose you mess up a commit message — we never do that, of course, but just pretend.

Clear up the confusion on the Git reflog vs. log debate. Git reflog tracks local commits on a repository while Git log tracks the entire commit history of a public repository.