Re: "git rebase" loses the additional changes in "evil" merges

From: Thomas Rast <trast@student.ethz.ch>
Date: Mar 4, 2013, 21:24 UTC
Message-ID: <87sj4aoo3s.fsf@pctrast.inf.ethz.ch>
In-Reply-To: <7vtxoqx3s1.fsf@alter.siamese.dyndns.org>

Junio C Hamano <gitster@pobox.com> writes:

Show 14 quoted lines

> worley@alum.mit.edu (Dale R. Worley) writes:
>
>> (git version 1.7.7.6)
>>
>> I've been learning how to use Git.  While exploring "git rebase", I've
>> discovered that if the branch being rebased contains an "evil" merge,
>> that is, a merge which contains changes that are in addition to the
>> changes in any of the parent commits, the rebase operation will
>> silenty lose those additional changes.
>
> I think this is to be expected for "git rebase", as it does not even
> look at merges.  It is a way to find non-merge commits that haven't
> been applied yet, and apply them to the upstream to create a new
> linear history.

I can see the problem with --preserve-merges though. It will actually just *redo* the merge; the name is wrong in the sense that it undertakes nothing to preserve whatever evilness was in it.

I suppose in theory it could first redo the merge on the original parents, and diff against the existing merge; that would be the evilness component. Then it could attempt to apply the same evilness on the new merge.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch