From: Jeff King <peff@peff.net>
Date: Tue, 06 Nov 2018 21:12:35 GMT
Subject: Re: [PATCH v2 1/1] pack-objects: ignore ambiguous object warnings
Message-ID: <20181106211234.GA8383@sigill.intra.peff.net>
In-Reply-To: <002868ee6bec3dac38749d0f05bf2db8da0969a5.1541536484.git.gitgitgadget@gmail.com>

On Tue, Nov 06, 2018 at 12:34:47PM -0800, Derrick Stolee via GitGitGadget wrote:

> From: Derrick Stolee <dstolee@microsoft.com>
> 
> A git push process runs several processes during its run, but one
> includes git send-pack which calls git pack-objects and passes
> the known have/wants into stdin using object ids. However, the
> default setting for core.warnAmbiguousRefs requires git pack-objects
> to check for ref names matching the ref_rev_parse_rules array in
> refs.c. This means that every object is triggering at least six
> "file exists?" queries.  When there are a lot of refs, this can
> add up significantly! I observed a simple push spending three
> seconds checking these paths.

Thanks, this fills out the details from the cover letter a bit better.

> The fix here is similar to 4c30d50 "rev-list: disable object/refname
> ambiguity check with --stdin". Save the value of the global
> warn_on_object_refname_ambiguity variable (which is usually set to
> the boolean config variable core.warnAmbiguousRefs) and change the
> state to false. Do this only during the get_object_list() method
> which reads the objects from stdin.

I think this parenthetical isn't quite right. We never change the value
of warn_on_object_refname_ambiguity based on user config. It's just that
if warn_ambiguous_refs is off, we do not even bother looking at the
object_refname variant.

So we'd never expect to see anything except "1" in our save_warning
variable. Doing a save/restore is just about code hygiene and
maintainability.

Other than that minor nit, this whole thing looks good to me.

-Peff