Re: [RFC PATCH 0/1] rebase --onto detection of already applied commits

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 13, 2022, 00:13 UTC
Message-ID: <xmqqlencqhxy.fsf@gitster.g>
In-Reply-To: <20221212113516.27816-1-cristian.ciocaltea@collabora.com>

Cristian Ciocaltea <cristian.ciocaltea@collabora.com> writes:

Show 6 quoted lines

> Let's consider the following operation:
>
>   git rebase --onto new-base upstream feature
>
> where 'feature' contains a few commits on top of 'upstream' which need to be
> rebased onto 'new-base'.

Isn't it what "git rebase new-base feature" for? "My 'feature' forked from where 'new-base' came from but they updated 'new-base' so I do not know if some of what I had in my 'feature' is in theirs. Please forward port what is still left in 'feature' on top of updated 'new-base' that I just got from them".

The primary reason why we have an explicit "--onto" is so that "rebase" is used just like

	git checkout --detach new-base
	git cherry-pick upstream..feature
	git checkout -B feature

to deal with a different situation, i.e. "My 'feature' forked from 'upstream', and I have a commit 'new-base'. Just transplant the whole thing on top of it", without having to worry about "what is already in new-base?" at all. After all, 'new-base' may not have ANY ancestry relationship with the 'upstream', so "inspect commits in the range upstream..new-base to exclude those that are the same as the ones in upstream..feature" is not a well defined operation.