Re: [PATCH v4 9/9] Documentation/config: add odb.<name>.promisorRemote

>> I do not think "sources that are not git repositories" is all that
>> interesting, unless they can also serve as the source for ext::
>> remote helper.  And if they can serve "git fetch ext::...", I think
>> they can be treated just like a normal Git repository by the
>> backfill code that needs to lazily populate the partial clone.
>
> I don't know about that. Imagine I had a regular Git repo with a bunch
> of large blobs, and then I also stored those large blobs in something
> like S3 that provides caching, geographic locality, and resumable
> transfers.
>
> It would be nice to be able to say:
>
>   1. Clone from the real repo, but do not transfer any blobs larger than
>      10MB.
>
>   2. When you need a blob, check the external odb that points to S3. Git
>      cannot know about this automatically, but presumably you would set
>      a few config variables to point to an external-odb helper script.
>
>   3. If for some reason S3 doesn't work, you can always request it from
>      the original repo. That part _doesn't_ need extra config, since we
>      can assume that the source of the promisor pack can feed us the
>      extra objects[1].
>
> But you don't need to ever be able to "git fetch" from the S3 repo.
>
> Now if you are arguing that the interface to the external-odb helper
> script should be that it _looks_ like upload-pack, but simply advertises
> no refs and will let you fetch any object, that makes more sense to me.
> It's not something you could "git clone", but you can "git fetch" from
> it.