Re: [PATCH v5 3/3] core: convert build-time USE_NSEC into runtime core.useNanosec

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

"D. Ben Knoble" <ben.knoble@gmail.com> writes:

> +		/* nanosecond timestamped files can also be racy! */
> +		(repo_config_values(istate->repo)->use_nanosec
> +		 ? (istate->timestamp.sec < sd->sd_mtime.sec ||
> +		    (istate->timestamp.sec == sd->sd_mtime.sec &&
> +		     istate->timestamp.nsec <= sd->sd_mtime.nsec))
> +		 : istate->timestamp.sec <= sd->sd_mtime.sec));
>  }

Currently this is probably fine, but the use of repo_config_values()
here means that the order in which we can transition/libify two
unrelated things are forced on us:

 * We'd first need to make sure repo_config_values() can work on an
   instance of repository that is not the_repository,

 * And until the above happens, we cannot do a --recurse-submodule
   option that loads the index in a submodule and operate on it in
   the same process (e.g., "git diff --resurse-submodules"),
   because immediately at this step, istate taken from a submodule
   would have its .repo member pointing at something that is not
   the_repository and we will hit a BUG().

And after writing all of the above, I realized that I am mostly
repeating what Patric already said in the upstream, e.g.,

    https://lore.kernel.org/git/an720tZnot07HYiK@pks.im/

Other than that, this looks good to me.