tl;dr: Git 2.54 and 2.55 introduced an experimental `git history` command with three subcommands—`fixup`, `reword`, and `split`—that let you amend, rename, or split older commits and automatically rebase all descendant branches atomically. It delivers several ergonomic wins commonly associated with jj (like updating refs across branches without leaving a broken state), though it refuses conflicting operations and doesn't yet support merge commits or first-class conflicts. It's built into core git, so no extra tooling is required.