Re: Fetch on submodule update

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Aug 6, 2018, 15:41 UTC
Message-ID: <20180806154122.GB105466@aiede.svl.corp.google.com>
In-Reply-To: <CAHd499CFHUwpNdYp2sMjChi_WWzSihi5VRzLMQbKsGrKf_Ktcg@mail.gmail.com>

Robert Dailey wrote:

Show 9 quoted lines

>                                                  Automatic would be
> great if submodules were treated as integrated in a similar manner to
> subtree, but it's not there. I wasn't aware that `submodule update`
> did a fetch, because sometimes if I do that, I get errors saying SHA1
> is not present (because the submodule did not get fetched). Granted I
> haven't seen this in a while, so maybe the fetch on submodule update
> is a newer feature. Do you know what triggers the fetch on update
> without --remote? Is it the missing SHA1 that triggers it, or is it
> fetching unconditionally?

Thanks for this and the rest of the context you sent. It's very helpful.

The relevant code in git-submodule.sh is

	# Run fetch only if $sha1 isn't present or it
	# is not reachable from a ref.
	is_tip_reachable "$sm_path" "$sha1" ||
	fetch_in_submodule "$sm_path" $depth ||
	say "$(eval_gettext "Unable to fetch in submodule path '\$displaypath'")"

	# Now we tried the usual fetch, but $sha1 may
	# not be reachable from any of the refs
	is_tip_reachable "$sm_path" "$sha1" ||
	fetch_in_submodule "$sm_path" $depth "$sha1" ||
	die "$(eval_gettext "Fetched in submodule path '\$displaypath', but it did not contain \$sha1. Direct fetching of that commit failed.")"

The fallback to fetching by SHA-1 was introduced in v2.8.0-rc0~9^2 (submodule: try harder to fetch needed sha1 by direct fetching sha1, 2018-02-23).

Jonathan