Re: Ideas to speed up repacking

>> * Scenario 4:
>>
>>    Starts with Setup 1.  Add some loose objects to the repo
>> via a local fast forward ref update (I am assuming this is
>> possible without adding any new unreferenced objects?)
>>
>>
>> In all 4 scenarios, I believe we should be able to skip
>> history traversal and simply grab all objects and repack
>> them into a new file?
>
> If nothing else has happened in the repository, perhaps, but I
> suspect that the real problem is how you would prove it.  For
> example, I am guessing that your Scenario 4 could be something like:
>
>     : setup #1
>     $ git repack -a -d -f
>     $ git prune
>
>     : scenario #4
>     $ git commit --allow-empty -m 'new commit'
>
> which would add a single loose object to the repository, advancing
> the current branch ref by one commit, fast-forwarding relative to
> the state you were in after setup #1.
>
> But how would you efficiently prove that it was the only thing that
> happened?

> Also with Scenario #2, how would you prove that the new pack does
> not contain any cruft that is not reachable?  When receiving a pack
> and updating our refs, we only prove that we have all the objects
> needed to complete updated refs---we do not reject packs with crufts
> that are not necessary.