Git 在功能分支上的 rebase master 后 rebase vs merge

Question

I'm learning about rebase and saw a workflow of doing a rebase on a feature branch and then merging it into master (as an example):

git checkout feature
git rebase master
git checkout master
git merge feature

However I saw another similar option of the last command being (instead of 'git merge feature'):

git rebase feature

How does the last part differ in this instance? Won't the result be the same linear timeline of the feature commits on top of master?

Answer 1

You may be learning about rebase, but I don't think you've quite understood it yet.

The command git rebase xxx means: rebase the branch I'm on now, onto xxx . It does not change xxx in any way.

This is confusing, because git merge xxx means exactly the opposite: it means, merge xxx into the branch I'm on now.

So for example if feature split off from master , and master had some commits and rebase had some commits, then git switch feature; git rebase master git switch feature; git rebase master changes the split-off point. That's effectively all it does.

If we start with this:

A -- B -- C -- D -- E (master)
           \
            X -- Y -- Z (feature)

Then git switch feature; git rebase master git switch feature; git rebase master results in this:

A -- B -- C -- D -- E (master)
                     \
                      X' -- Y' -- Z' (feature)

(Note the use of the "prime" marker on the moved commits, because you cannot actually move a commit; these commits are copies of the original X, Y, and Z.)

Answer 2

How does the last part differ in this instance?

In this case, there is no difference. Any of these statements could be the 4th command and the results would be the same:

git merge feature
# or
git rebase feature
# or
git reset --hard feature
# or
git checkout -B master feature

Since we're rebasing in a playful manner, note the 4 commands could be reduced to two too ² :

git rebase master feature
git switch -C master feature

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² Did I really just do that?