Re: [PATCH 1/2] submodule: Include check for objects when fetching

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

Junio C Hamano <gitster@pobox.com> writes:

> Junio C Hamano <gitster@pobox.com> writes:
>
>> Stefan Beller <sbeller@google.com> writes:
>>
>>> Junio wrote:
>>>> To be complete, the rev-list command line should also run with
>>>> "--objects"; after all, a commit walker fetch may have downloaded
>>>> commit chain completely but haven't fetched necessary trees and
>>>> blobs when it was killed, and "rev-list $sha1 --not --all" would not
>>>> catch such a breakage without "--objects".
>>>
>>> By adding the --objects switch to rev-list we make sure to do a complete
>>> check.
>>
>> You also need to drop "-n1" for the command to be equivalent to
>> quickfetch, I think.
>
> Ahh, I think I need to take it back.
>
> As the existing code relies not just on the exit status of rev-list
> but also checks if anything comes out of it, having "-n1" would not
> hurt.
>
> The case I was worried about was that we have all commits to connect
> $sha1 to what are reachable from refs, but some tree/blob objects
> referenced by these commits were missing.  By cutting the displaying
> with "-n1", rev-list may happily exit successfully after showing $sha1,
> without even realizing that some trees/blobs are missing and the history
> leading to $sha1 cannot be considered complete.
>
> But because the code checks the empty-ness of $rev, this case is diagnosed
> as "$sha1 is not reachable from any of the refs" correctly anyway,
> so it should be OK.

... this is embarrassing, but for exactly the same reason, I do not
think we need "--objects" either.  If $sha1 is not something that is
already reachable from any of the refs, "rev-list -n1" would show
something, making $rev non-empty, and it would result in a fetch,
whether the objects that are reachable from the commits between
existing refs and $sha1 are complete or not.  So it is pointless to
use "--objects" to test their presense.

Sorry about the noise ;-)

>>> Signed-off-by: Stefan Beller <sbeller@google.com>
>>> ---
>>>  git-submodule.sh | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/git-submodule.sh b/git-submodule.sh
>>> index 9bc5c5f..f5d6675 100755
>>> --- a/git-submodule.sh
>>> +++ b/git-submodule.sh
>>> @@ -746,7 +746,7 @@ Maybe you want to use 'update --init'?")"
>>>  				# Run fetch only if $sha1 isn't present or it
>>>  				# is not reachable from a ref.
>>>  				(clear_local_git_env; cd "$sm_path" &&
>>> -					( (rev=$(git rev-list -n 1 $sha1 --not --all 2>/dev/null) &&
>>> +					( (rev=$(git rev-list --objects -n 1 $sha1 --not --all 2>/dev/null) &&
>>>  					 test -z "$rev") || git-fetch)) ||
>>>  				die "$(eval_gettext "Unable to fetch in submodule path '\$displaypath'")"
>>>  			fi