Re: [PATCH 06/10] rev-list: add --allow-partial option to relax connectivity checks

[Jeff Hostetler <git@jeffhostetler.com>]

On 3/8/2017 1:55 PM, Junio C Hamano wrote:
> Jeff Hostetler <jeffhost@microsoft.com> writes:
>
>> From: Jeff Hostetler <git@jeffhostetler.com>
>>
>> Teach rev-list to optionally not complain when there are missing
>> blobs.  This is for use following a partial clone or fetch when
>> the server omitted certain blobs.
>
> This makes it impossible to tell from objects missing by design
> (because we did an --partial-by-size clone earlier, expecting we can
> later fetch from elsewhere when necessary) and objects inaccessible
> by accident (because you have a repository corruption), no?

Right.  It will effectively neuter several commands like
index-pack, gc, and fsck WRT missing blobs.

> Even though I do very much like the basic "high level" premise to
> omit often useless large blobs that are buried deep in the history
> we would not necessarily need from the initial cloning and
> subsequent fetches, I find it somewhat disturbing that the code
> "Assume"s that any missing blob is due to an previous partial clone.
> Adding this option smells like telling the users that they are not
> supposed to run "git fsck" because a partially cloned repository is
> inherently a corrupt repository.
>
> Can't we do a bit better?  If we want to make the world safer again,
> what additional complexity is required to allow us to tell the
> "missing by design" and "corrupt repository" apart?

I'm open to suggestions here.  It would be nice to extend the
fetch-pack/upload-pack protocol to return a list of the SHAa
(and maybe the sizes) of the omitted blobs, so that a partial
clone or fetch would still be able to be integrity checked.

Jeff