Rebase

A merge joins two histories and leaves the fork visible forever. A rebase does something different: it replays your commits on top of the other branch, as if you had started from there all along.

The result is a straight line instead of a fork. But notice what it costs — the replayed commits are brand new commits with new ids. The originals are left behind.

That is why the rule of thumb is: rebase your own unshared work, merge when others already have the commits.

Exercises

1. Exercise 1. main and feature have each moved on. Rebase feature onto main so its commit replays on top of main's tip.
2. Exercise 2. feature now has two commits of its own. Rebase again — both get replayed, in order, and both get new ids.