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Fri, 20 Mar 2026 03:35:39 -0400 (EDT) Received: by mail (OpenSMTPD) with ESMTPSA id 23ac6bf9 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Fri, 20 Mar 2026 07:35:37 +0000 (UTC) Date: Fri, 20 Mar 2026 08:35:34 +0100 From: Patrick Steinhardt To: Derrick Stolee Cc: Derrick Stolee via GitGitGadget , git@vger.kernel.org, gitster@pobox.com Subject: Re: [PATCH 0/5] backfill: accept revision arguments Message-ID: References: <29ec9e5f-ad14-4a87-92f9-a3ffa4077f69@gmail.com> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29ec9e5f-ad14-4a87-92f9-a3ffa4077f69@gmail.com> On Thu, Mar 19, 2026 at 08:59:01AM -0400, Derrick Stolee wrote: > On 3/19/2026 5:54 AM, Patrick Steinhardt wrote: > > I think especially blaming is a bit of a sore spot -- downloading blobs > > one by one simply doesn't cut it there. I wonder whether we can easily > > use the backfill mechanism to fetch blobs automatically in git-blame(1) > > so that the user doesn't need to know about git-backfill(1) at all? > > I've thought about this a bit, and I'm not sure that we want to run > 'git backfill' directly. Instead, it would be nice if we did a "staged" > algorithm for 'git blame': > > 1. Walk commits according to the pathspec to collect the commits that > changed the path. > > 2. Collect the list of blob OIDs that will be needed for computing diffs > for the line-tracking algorithm. > > 3. In batches, download groups of missing blobs and then process them > for line-tracking diffs. (Stop if all lines are blamed; continue to > next batch if more lines are needed.) > > This would be a significant rewrite of the blame algorithm, though. I > briefly considered this approach about a year ago and decided it would > be easier to start with 'git backfill' and see whether that satisfies > most needs. > > The biggest reason to maybe avoid 'git backfill HEAD -- ' before > _every_ blame operation is that this will add overhead on repeated > calls that may be obnoxious in its own way. Maybe doing an opt-in > 'git blame --backfill ' would make it easier for users to opt-in > when they want to. That's fair. I fully agree that just blindly doing this would be likely be inefficient. Ideally, the batching logic would only kick in whenever we see a missing object. Anyway, this definitely doesn't have to be part of this series, I was mostly wondering how hard it is to do. Thanks! Patrick