Re: [PATCH 05/11] maintenance: add commit-graph task

From: "Martin Ågren" <martin.agren@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>,
	"Git Mailing List" <git@vger.kernel.org>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	"Josh Steadmon" <steadmon@google.com>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Jeff King" <peff@peff.net>,
	"Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
	"Phillip Wood" <phillip.wood123@gmail.com>,
	"Emily Shaffer" <emilyshaffer@google.com>,
	sluongng@gmail.com, "Jonathan Tan" <jonathantanmy@google.com>,
	"Derrick Stolee" <derrickstolee@github.com>,
	"Derrick Stolee" <dstolee@microsoft.com>
Subject: Re: [PATCH 05/11] maintenance: add commit-graph task
Date: Fri, 14 Aug 2020 14:23:05 +0200	[thread overview]
Message-ID: <CAN0heSqoPAx84-o2JKSjM6b+Jp2rk_j6p68iJg30AGDa+6HeeA@mail.gmail.com> (raw)
In-Reply-To: <0380dcbf-82a0-68d0-b421-9f5c5a640ab5@gmail.com>

On Wed, 12 Aug 2020 at 15:30, Derrick Stolee <stolee@gmail.com> wrote:
>
> On 8/7/2020 6:29 PM, Martin Ågren wrote:
> > On Thu, 6 Aug 2020 at 18:50, Derrick Stolee via GitGitGadget
> > <gitgitgadget@gmail.com> wrote:
> >> diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
> >> index 089fa4cedc..35b0be7d40 100644
> >> --- a/Documentation/git-maintenance.txt
> >> +++ b/Documentation/git-maintenance.txt
> >> @@ -35,6 +35,24 @@ run::
> >>  TASKS
> >>  -----
> >>
> >> +commit-graph::
> >> +       The `commit-graph` job updates the `commit-graph` files incrementally,
> >> +       then verifies that the written data is correct. If the new layer has an
> >> +       issue, then the chain file is removed and the `commit-graph` is
> >> +       rewritten from scratch.
> >> ++
> >> +The verification only checks the top layer of the `commit-graph` chain.
> >> +If the incremental write merged the new commits with at least one
> >> +existing layer, then there is potential for on-disk corruption being
> >> +carried forward into the new file. This will be noticed and the new
> >> +commit-graph file will be clean as Git reparses the commit data from
> >> +the object database.
> >
> > This reads somewhat awkwardly. I think what you mean is something like
> > "is there a risk for on-disk corruption? yes, but no: we're clever
> > enough to detect it and avoid it". So from a user's point of view, I
> > think this is too detailed.

[snip quite a bit]

> Back to the point of your comments: I'm not sure this second paragraph
> is required at all in the documentation. The first paragraph already
> says:
>
>         ...then verifies that the written data is correct.
>
> This "written data" _is_ the top layer of the chain. There is probably
> no reason to dig deeper into _why_ we do this in this user-facing
> documentation.
>
> So, I propose just deleting this paragraph. What do you think?

Yeah, that makes lots of sense. Thanks!

Martin