Re: [BUG?] inconsistent `git reflog show` output, possibly `git fsck` output

From: Keshav Kini <keshav.kini@gmail.com>
Date: Oct 28, 2013, 17:16 UTC
Message-ID: <8761shjoyx.fsf@gmail.com>
In-Reply-To: <xmqqtxgib1qm.fsf@gitster.dls.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 15 quoted lines

> Roberto Tyley <roberto.tyley@gmail.com> writes:
>> On 21/09/2013 23:16, Keshav Kini wrote:
>>> [SNIP]
>>> This situation came about because the BFG Repo-Cleaner doesn't write new
>>> reflog entries after creating its new objects and moving refs around.
>>
>> True enough - I don't think the BFG does write new entires to the
>> reflog when it does the final ref-update, and it would be nicer if it
>> did. I'll get that fixed.
>
> (sorry for replying late)
>
> So this can be closed as "BFG not writing reflog in a consistent
> way, and 'git reflog show' is acting GIGO way"?  Or was there
> something the core side needs to do?

Hi Junio,

Below I'm resending a mail that I sent to the list earlier, but not to you or Roberto personally, as I just realized. So in case you didn't see it before, here it is -- if you did see it before, sorry for the noise.

Hi Junio,

Thanks for your reply. In my original mail, immediately after the snippet Roberto quoted above, I said, "But that aside, I think how git handles the situation might be a bug." To wit:

Show 12 quoted lines

> It seems to me that one of two things should be the case. Either 1) it
> should be considered impossible to have a reflog for a ref X which
> doesn't contain a chain of commits leading up to the current location of
> X; or 2) if reflogs are allowed not to form an unbroken chain of commits
> leading to X, then `git reflog show` should at least make sure to
> actually display a commit ID corresponding to the second field of each
> reflog entry it reads, and not some other commit ID.
> 
> In the first case, the bug is that `git fsck` doesn't catch the
> supposedly impossible situation that exists in the repository I've
> described in this email. In the second case, the bug is that `git reflog
> show` has bad output.

Before this is closed, I would appreciate it if I could get some feedback from git developers on the above two paragraphs.

Thanks,
    Keshav