Re: [PATCH v2 0/1] rev-list: add --missing-only option to filter output

[Junio C Hamano <gitster@pobox.com>]

Siddharth Asthana <siddharthasthana31@gmail.com> writes:

> At GitLab, Gitaly uses rev-list --missing=print on partial clones to
> find missing objects. The output mixes present and missing objects and
> prefixes missing ones with '?', so we post-process it. --missing-only
> avoids that.

Not an objection to the feature (as it can already be done with
post-processing), but stepping back a bit, how is this list of
missing objects used?

You know what objects you currently have.  They refer to other
objects, some of which you may lack.  You can get a list of them,
and then what?  After fetching them from 'origin', you will have
a new set of missing objects (e.g., after fetching a missing
commit, its parents become known and missing; after fetching a
missing tree, the blobs and trees contained in it become known
and missing).

Fetching missing objects a batch at a time sounds like too much
back-and-forth to peel the onion, if the process using
'--missing-only' is trying to find out what it wants to fetch,
and would be a rather inefficient way to backfill a shallow
clone.  So I wonder how this fits into the larger picture.

Thanks.