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-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 836231F531 for ; Fri, 7 Aug 2020 22:35:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726066AbgHGWfX (ORCPT ); Fri, 7 Aug 2020 18:35:23 -0400 Received: from cloud.peff.net ([104.130.231.41]:52450 "EHLO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726015AbgHGWfX (ORCPT ); Fri, 7 Aug 2020 18:35:23 -0400 Received: (qmail 3149 invoked by uid 109); 7 Aug 2020 22:35:23 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with ESMTP; Fri, 07 Aug 2020 22:35:23 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 19191 invoked by uid 111); 7 Aug 2020 22:35:22 -0000 Received: from coredump.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.2) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Fri, 07 Aug 2020 18:35:22 -0400 Authentication-Results: peff.net; auth=none Date: Fri, 7 Aug 2020 18:35:22 -0400 From: Jeff King To: Junio C Hamano Cc: Nuthan Munaiah , git@vger.kernel.org Subject: Re: `git blame` Line Number Off-by-one Message-ID: <20200807223522.GB3750245@coredump.intra.peff.net> References: <20200807212159.GA1871940@coredump.intra.peff.net> <20200807213349.GB1871940@coredump.intra.peff.net> <20200807222630.GA3750245@coredump.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200807222630.GA3750245@coredump.intra.peff.net> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Aug 07, 2020 at 06:26:30PM -0400, Jeff King wrote: > On Fri, Aug 07, 2020 at 03:05:27PM -0700, Junio C Hamano wrote: > > > Jeff King writes: > > > > > Dropping it entirely, as below, doesn't break any tests. Junio, do you > > > know of a case this is meant to improve? > > > > I think the only conceivable case is that in the middle of a single > > block of text in an ancient version, another block of lines gets > > inserted during the evolution of the file, but in the end these > > intermediate edits all go away and the same original text remains. > > > > In such a case, without coalescing, we would not treat the original > > single block of text as a single unit. > > Yeah, that makes sense, and it should be possible to construct a case > based on that. It was even easier than I expected. :) Try this: git init repo cd repo seq 20 >file git add file git commit -m base { seq 10; echo foo; seq 11 20; } >file git commit -am cruft seq 20 >file git commit -am revert git blame --root --porcelain file With the coalescing, we get a single 20-line block: 25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 1 1 20 author Jeff King ... 1 ... 25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 11 11 11 and without it, we get two 10-line blocks: 25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 1 1 10 author Jeff King ... 1 ... 25d93ad4c4b27570ccd4b6412ccaa549ae6f9ff7 11 11 10 11 I doubt it really matters all that much in practice, but it's possible some consumer of --porcelain relies on us giving minimal blocks. So that argues for fixing blame_coalesce() to make sure that we coalesce only when the blocks are adjacent in both the source and the result. Otherwise we're losing information. -Peff