Re: [PATCH v2 05/11] maintenance: add commit-graph task

[Jonathan Tan <jonathantanmy@google.com>]

> The cases we've seen this happen were root-caused to hardware
> problems (disk or RAM), and the invalid data was present immediately
> after the "git commit-graph write" command. Since implementing the
> "verify" step after each write, we have not had any user reports of
> problems with these files.
> 
> Are you suggesting one of these options?
> 
>  1. Remove this validation and rewrite entirely.
> 
>  2. Remove the rewrite and only delete the known-bad data.
> 
>  3. Insert a way to cause the verify to return failure mid-process,
>     so that this function can be covered by tests.

I was suggesting 1, although 2 and 3 would assuage my concerns also (2
less so, but just deleting the file is relatively simple and easier to
reason about). I don't think Git in general defends much against
hardware problems, but if an issue is noticeable in some hardware (as is
in this case, at least in the past) I can see why we would want to
defend against it. My concern is that if we do defend against it, but
leave it untested, several versions of Git later we might find that we
need this defense but it does not work.