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From: Junio C Hamano <gitster@pobox.com>
To: Alban Gruin <alban.gruin@gmail.com>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
	git@vger.kernel.org, "Elijah Newren" <newren@gmail.com>,
	"Ævar Arnfjörð" <avarab@gmail.com>,
	"Eugeniu Rosca" <erosca@de.adit-jv.com>,
	"Jeff King" <peff@peff.net>,
	"Eugeniu Rosca" <roscaeugeniu@gmail.com>
Subject: Re: [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase
Date: Wed, 22 Jan 2020 12:47:22 -0800
Message-ID: <xmqq5zh36wx1.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20200121191857.23047-1-alban.gruin@gmail.com> (Alban Gruin's message of "Tue, 21 Jan 2020 20:18:57 +0100")

Alban Gruin <alban.gruin@gmail.com> writes:

> One of the first things done by the interactive rebase is to make a todo
> list.  This requires knowledge of the commit range to rebase.  To get
> the oid of the last commit of the range, the tip of the branch to rebase
> is checked out with prepare_branch_to_be_rebased(), then the oid of the
> HEAD is read.  On big repositories, it's a performance penalty: the user
> may have to wait before editing the todo list while git is extracting the
> branch silently (because git-checkout is silenced here).  After this,
> the head of the branch is not even modified.

Hmph.  One curious thing in the above is why this is specific to
"rebase -i". The need to know the commit range to rebase is shared
across any rebase backend, and it would be the most natural to parse
the optional second argument (i.e. the branch or the commit to
rebase) before builtin/rebase.c dispatches to a specific rebase
backend, wouldn't it?  So, the question is why a normal "rebase"
does not need the same fix?

If the answer is "rebase in general was fine without extra checkout,
but 'rebase -i' was doing an unnecessary checkout" (or any other
answer) that is something that would help future readers to record
in the commit log message.

Thanks.



  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-08 21:43 Unreliable 'git rebase --onto' Eugeniu Rosca
2020-01-08 22:35 ` SZEDER Gábor
2020-01-09  0:55   ` Elijah Newren
2020-01-09 15:03     ` SZEDER Gábor
2020-01-09 17:53       ` Elijah Newren
2020-01-21 19:18       ` [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase Alban Gruin
2020-01-21 20:07         ` Elijah Newren
2020-01-22 20:24         ` Junio C Hamano
2020-01-22 20:47         ` Junio C Hamano [this message]
2020-01-24 14:45           ` Alban Gruin
2020-01-24 14:45         ` [PATCH v2] " Alban Gruin
2020-01-24 14:55           ` Alban Gruin
2020-01-24 18:12             ` Junio C Hamano
2020-01-24 15:05           ` [PATCH v3] " Alban Gruin
2020-01-24 18:30             ` Junio C Hamano
2020-02-05 14:31             ` Johannes Schindelin
2020-01-24 17:11           ` [PATCH v2] " Andrei Rybak
2020-01-09 11:13   ` Unreliable 'git rebase --onto' Eugeniu Rosca
     [not found] ` <CABPp-BHsyMOz+hi7EYoAnAWfzms7FRfwqCoarnu8H+vyDoN6SQ@mail.gmail.com>
2020-01-09 10:53   ` Eugeniu Rosca
2020-01-09 18:05     ` Elijah Newren
2020-01-10  0:06       ` Eugeniu Rosca
2020-01-10  2:35         ` Elijah Newren

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