From: David Gudeman
Sent: Thursday, June 13, 2013 7:12 PM
Subject: [git-users] what is the point of rebase?
I've been getting to know git recently as part of some work I needed to do,
and I love the easy branching and merging, but I have to admit that rebase is
confusing me. I'm not confused about what it does (I don't think); I'm confused
about what the point is. As far as I can tell, rebase is just the same as doing
a merge and then throwing away some history. Why throw away the history? All of
the documentation I can find just refers to making history "clean", but the
history doesn't have to actually BE clean to LOOK clean. So why?
Or here is another way to ask the question. Suppose git repositories had a
special flag that you could put on a branch that said, "don't show this branch
in histories or push it or allow it to be pulled unless the user does something
special to ask for hidden branches". Then suppose git had a merge-and-hide
command that would do a merge and then set this flag on the topic branch to
effectively hide it unless the user really wants to see it. What does rebase
accomplish that merge-and-hide would not?
I keep feeling that there must be something else, otherwise why deal with the
potential negative consequences of deleting history unrecoverably? All of the
documentation on rebase talks about the problem of rebasing a branch out from
under someone who is still working on it. So what is the advantage of rebase
over merge-and-hide that makes it worth dealing with this problem.
Rebase is a way, within a distributed system, of noticing that the world has
moved on since you started on your magic topic branch.
So you want your magic topic branch to cleanly apply to the New World Order of
the upstream repo, hence you 'rebase', or transfer, your series of nice small
changes (commits) to the latest upstream reference point (often tip of
master/production), and while doing the rebase, you fix all the conflicts (with
the NWO changes) as you go to create a clean sequence, and then you will have a
commit/patch series that can either be fast forward applied, or merged without
Obviously (?), having done your rebase you will have to style check, compile
and test you new magic code to see if it actually works as planned without any
regressions (and fix a few minor mistakes). By which time the NWO has moved on
again, so another quick rebase gets you to the head of the queue, and you are
awarded tea and medals.
The other scenario is that you are working on say git itself and you send in
patches for review, which end up with fixups and comments, so you have to
continue to rebase your own work forward to the relevant start point,
especially if there is an overlap with other patch series.
The "problem" doesn't exist in other, non-distributed, systems because of the
restrictive check-out - check-in process which nails both feet to the floor to
stop you going round in circles (and limits progress!). Rebase lets you leap
ahead and catch up with the latest and greatest code release, or a
collaborators code, or wherever.
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