In git, what is the difference between merge --squash and rebase?

问题:

I'm new to git and I'm trying to understand the difference between a squash and a rebase. As I understand it you perform a squash when doing a rebase.

回答1:

Both git merge --squash and git rebase --interactive can produce a "squashed" commit.
But they serve different purposes.

• git merge --squash abranch

will produce a squashed commit on the destination branch, without marking any merge relationship.
(Note: it does not produce a commit right away: you need an additional git commit -m "squash branch")
This is useful if you want to throw away the source branch completely, going from (schema taken from SO question):

 git checkout stable        X                   stable      /                    a---b---c---d---e---f---g tmp 

to:

git merge --squash tmp git commit -m "squash tmp"        X-------------------G stable      /                    a---b---c---d---e---f---g tmp 

and then deleting tmp branch.

• git rebase --interactive

replays some or all of your commits on a new base, allowing you to squash (or more recently "fix up", see this SO question), going directly to:

git checkout tmp git rebase -i stable        stable       X-------------------G tmp      /                      a---b 

If you choose to squash all commits of tmp (but, contrary to merge --squash, you can choose to replay some, and squashing others).

So the differences are:

• merge does not touch your source branch (tmp here) and creates a single commit where you want.
• rebase allows you to go on on the same source branch (still tmp) with:
  • a new base
  • a cleaner history

回答2:

Merge squash merges a tree (a sequence of commits) into a single commit. That is, it squashes all changes made in n commits into a single commit.

Rebasing is re-basing, that is, choosing a new base (parent commit) for a tree. Maybe the mercurial term for this is more clear: they call it transplant because it's just that: picking a new ground (parent commit, root) for a tree.

When doing an interactive rebase, you're given the option to either squash, pick, edit or skip the commits you are going to rebase.

Hope that was clear!

回答3:

Merge commits: retains all of the commits in your branch and interleaves them with commits on the base branch

Merge Squash: retains the changes but omits the individual commits from history

Rebase: This moves the entire feature branch to begin on the tip of the master branch, effectively incorporating all of the new commits in master

More on here

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