git rebase

git rebase <base> takes the commits of the current branch from its common ancestor with <base> up to HEAD, and replants them on top of <base>. Each commit gets a new parent, so each commit gets a new SHA.

Basic scenario

before:  main:  A → B → E

                   \

         feat:      C → D

git switch feat

git rebase main

after:   main:  A → B → E

                        \

         feat:              C' → D'    ← new SHAs

The changes in C' and D' are the same as in C and D. But they are different objects: for Git they are new commits.

When to use it

• Before a PR, so the feature branch sits on top of a fresh main with no merge commits.
• Cleaning up local history via rebase -i (see interactive-rebase).
• Moving a branch to a different base with --onto.

The main rule

Do not rebase public branches. If someone has cloned the branch, they still have the old SHAs. After your force-push their history diverges. Rebase is safe only on your personal feature branch, before or immediately after review.

Conflicts

If a conflict occurs on any commit, Git stops, marks the conflicting files, and waits for you to resolve them:

# edit the files, remove the markers

git add <files>

git rebase --continue      # continue with the next commit

# or skip the current commit:

git rebase --skip

# or cancel everything:

git rebase --abort

A conflict can appear on every commit in a row if each one touches the disputed lines. After rebase each intermediate result is already clean.

After rebase

If the branch was already pushed, a plain push will be rejected because the SHAs changed:

git push --force-with-lease

--force-with-lease verifies that the remote has not moved forward (no one else pushed in the meantime). Always prefer --force-with-lease over --force.

Pitfalls

• Rebase copies author dates as-is but updates committer dates. After a rebase, git log --pretty=fuller may show seemingly odd discrepancies between the two.
• On a large number of commits, rebase can take noticeable time and may require resolving conflicts at each step.
• git pull --rebase combines fetch with a rebase of your local commits on top of the remote ones. A useful default: git config --global pull.rebase true.