# Merging ## Overview **Merging** (also called “delta rebasing”) is the process of taking all Ubuntu changes ([Ubuntu delta](https://documentation.ubuntu.com/project/how-ubuntu-is-made/concepts/glossary.md#term-Ubuntu-Delta)) made on top of one Debian version of a package and re-doing them on top of a new Debian version of the package. See [Merges & syncs](https://documentation.ubuntu.com/project/how-ubuntu-is-made/processes/merges-and-syncs.md#merges-syncs) for more context information. This is not to be confused with a **git merge**, wherein two diverging branches are reconciled together. The Ubuntu merge process (counter-intuitively) does not directly involve a git merge. The following diagram compares a standard git merge with an Ubuntu merge:  Merging is done using the `git-ubuntu` tool and is quite similar to a standard `git rebase` where commits from one point are replayed on top of another point. At a more detailed level, there are other sub-tasks to be done, including: * Splitting large, “omnibus”-style commits into smaller logical units (one commit per logical unit). * Harmonizing `debian/changelog` commits into two commits: a changelog merge and a reconstruction. With this process, we keep the Ubuntu version of a package cleanly applied to the end of the latest Debian version and make it easy to drop changes as they become redundant. ## Merge-o-Matic For a list of packages that have changed in Debian but not merged into Ubuntu, see the Merge-o-Matic tool: * [main](https://merges.ubuntu.com/main.html) * [universe](https://merges.ubuntu.com/universe.html) * [restricted](https://merges.ubuntu.com/restricted.html) * [multiverse](https://merges.ubuntu.com/multiverse.html)