Re: [PATCH v3] fetch: delay fetch_if_missing=0 until after config

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 29, 2019, 01:39 UTC
Message-ID: <xmqqh83s8h3m.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20191025174129.194010-1-jonathantanmy@google.com>

Jonathan Tan <jonathantanmy@google.com> writes:

Show 11 quoted lines

>> > Instead, we can control whether a region of code lazy-fetches...
>> 
>> The approach "from here to there, we can set global to forbid
>> lazy-fetch" may prolong the life support of the quick-and-dirty
>> mechanism, but it has to assume you can say "from here to there"; it
>> would mean that we cannot go multi-threaded until we get off of it.
>
> By "from here to there", I meant, for example, creating a struct
> repository in cmd_fetch() that has fetch_if_missing=0, then passing that
> repository to fetch_pack() (once fetch_pack() and all functions it calls
> support a repository object).

I know---but that means the struct cannot be shared among threads that are calling object layer, some of which want to lazily fetch missing objects while others only want to check the existence, at the same time.

Compared to that, judicious use of OBJECT_INFO_SKIP_FETCH_OBJECT and other flags by callers can tell the underlying machinery why we are interested in the object, which I think is the right direction to go in the longer term. What I am not certain about is if we are ready to move to the right direction for the longer term, or we should still be relying on the big-hammer global bit for expediency a bit longer.