From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 602321F87F for ; Mon, 19 Nov 2018 02:15:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727694AbeKSMhU (ORCPT ); Mon, 19 Nov 2018 07:37:20 -0500 Received: from pb-smtp1.pobox.com ([64.147.108.70]:57017 "EHLO pb-smtp1.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726861AbeKSMhU (ORCPT ); Mon, 19 Nov 2018 07:37:20 -0500 Received: from pb-smtp1.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 08B9912228D; Sun, 18 Nov 2018 21:15:12 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=UouTboBgWUxWO/zYp2UwbGzCwf4=; b=qd8I2i rS/O7OtpTwyliuAJnyY4WqnUT9LqWIyWN0MJ4x8KfSHTKtfDDxtwiyfOg2kFsJDh FsUpRx/MMwLkv9XdqFyyr28N/AP+jdHgFqX4Q9C/PJBnZLFROPHwAA3FmM6fjfh5 yGHEWckx3YdkfJQS5U5U6h4GxEwcSaSGQWPkU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=UmVYW7m7m0tcYLAi6jBdzPJ/jla+E9RP XELUdUSuvUpALQuU5YklCAIS3jJ4gMCNgdZN+AbGEfErFPSwKRVc6C2D8j1GKecX Q2ikSG7tehggesQcqShd9zpFKdHs9SeF1v5fUTSi7+nDAmLciQNM5cOE1R8wkBAQ aVsKTdlGAf0= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id F262D12228B; Sun, 18 Nov 2018 21:15:11 -0500 (EST) Received: from pobox.com (unknown [35.187.50.168]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id 6E6E1122289; Sun, 18 Nov 2018 21:15:11 -0500 (EST) From: Junio C Hamano To: Stefan Xenos Cc: git@vger.kernel.org, Stefan Beller , Jonathan Nieder , Junio C Hamano , Jonathan Tan , Derrick Stolee , Carl Baldwin , Dave Borowitz Subject: Re: [PATCH] technical doc: add a design doc for the evolve command References: <20181115005546.212538-1-sxenos@google.com> Date: Mon, 19 Nov 2018 11:15:10 +0900 In-Reply-To: (Stefan Xenos's message of "Sun, 18 Nov 2018 16:36:43 -0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: F18D2D82-EBA0-11E8-8FBD-063AD72159A7-77302942!pb-smtp1.pobox.com Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Stefan Xenos writes: >> And the other half is that while I consider the "origin" thing is >> unnecessary for the above reasons, having it means we need to not >> just transfer the history reading to aa7ce555 and d664309ee (which >> are necessary anyway while we have histories to transplant from >> d664309ee to aa7ce555) but also have to pull in the history leading >> to 7e1bbcd and we cannot discard it. > > I'll assume that by "history" you're referring to the change graph > (the metacommits) and not the branches (the commits), which would have > no origin edges or connection between replacements. I meant the project's history, not the meta-graph thing. By having a "this was cherry-picked from that commit" in a commit that is not GC'ed, the original commit that has no longer have any relevance (because the newer one that is the result of the cherry-pick is the surviving version people will be building on) is kept reachable. It is very much delierate that "cherry-pick -x" does not make the "origin" reachable and merely notes it in the human readable form that is ignored by the reachablity machinery. > If the user has kept a change around in their metas namespace, it's an > indication that they (or their collaborators) are still working on it > and want its history to be retained. This is where we differ. If commit X was rewritten (perhaps with help from change cherry-picked from commit Z, or without any) to produce Y, I do agree that it would be logical to keep X around until every dependent commit on it are migrated to be on top of Y. But we do not need Z to transplant what used to be on X on top of Y, do we? So I do agree that in such a situation they want the relevant parts of the history retained, but I do not agree that "origin" is among them. Side note. As long as we have commits yet to be migrated to be on Y that still is on X, ew do not need the meta-commit to be protecting from getting GC'ed, as X is reachable from these "need to be updated" branch tips anyway. What we gain from extra reachability brought in by the meta commits is that by fetching the "change", we get Y (and its anestors), even if we are not following any branch that contains it, so that we can migrate those that are still based on X to it.