Re: Fetch on submodule update

[Robert Dailey <rcdailey.lists@gmail.com>]

On Mon, Aug 6, 2018 at 10:41 AM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Robert Dailey wrote:
>
>>                                                  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).

Yep, that's the root cause; I was basing my concerns on a legacy
issue. I just had avoided using `update` when I expected a fetch, so I
never saw the issue again, and thus didn't realize it was corrected.
Very helpful. Thanks again!