Re: [PATCH v2 0/5] Fsck for lazy objects, and (now) actual invocation of loader

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 2, 2017, 16:20 UTC
Message-ID: <xmqqefsudjqk.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170801171944.7690a63f@twelve2.svl.corp.google.com>

Jonathan Tan <jonathantanmy@google.com> writes:

> One possibility to conceptually have the same thing without the overhead
> of the list is to put the obtained-from-elsewhere objects into its own
> alternate object store, so that we can distinguish the two.

Now you are talking. Either a separate object store, or a packfile that is specially marked as such, would work. "Maintaining a list of object names in a flat file is too costly" is not a valid excuse to discard the integrity of locally created objects, without which Git will no longer be a version control system, and your "We have to trust the sender of objects on the other side anyway when operating in lazy-objects mode, so devise a way that we can use to tell which objects we _know_ the other side has" that leads to the above idea is a good line of thought.

Show 5 quoted lines

> I mentioned
> this in my e-mail but rejected it, but after some more thought, this
> might be sufficient - we might still need to iterate through every
> object to know exactly what we can assume the remote to have, but the
> "frontier" solution also needs this iteration, so we are no worse off.

Most importantly, this is allowed to be costly---we are doing this not at runtime all the time, but when the user says "make sure that I haven't lost objects and it is safe for me to build further on what I created locally so far" by running "git fsck".