Re: ps/receive-use-only-advertised

Jeff King [off-list ref] writes:

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 "git receive-pack" used to use all the local refs as the boundary
 for checking connectivity of the data "git push" sent, but now it
 uses only the refs that it advertised to the pusher.  In a
 repository with the .hideRefs configuration, this reduces the
 resource needed to perform the check, and also forces the pusher to
 prove they have all objects that are necessary to complete the
 history on top of only the history available to them.

We have at a later point established that this is not true: the pusher
does not have to prove they have all objects. As the `--not --all` part
in git-rev-list(1) is merely an optimization the semantics aren't
changed at all

Thanks; this is Junio's description from when he picked up the topic
back in WC #08 from October. I'll need to update before graduating it
down.

Yeah, I think you can probably just remove everything from "and also
forces..." on.

Hmph, --not --all is a way to make the rev-list error out if the
proposed new tips are not connected with existing objects to the
"existing" refs, and I thought that removing "hidden" ones from
"--all" means that the pusher is now forced to push objects all
needed.  But you are right.  Excluding the hidden refs from "--all"
while doing the "rev-list new-tip --not --all" traversal does not
exclude pre-existing objects that are only reachable from these
hidden refs in the object store, so it does not help ensure that the
pusher has to prove they have these objects.