Re: 2.22.0 repack -a duplicating pack contents

> I can't think of some great solution for this case, some thoughts:
> 
>  a. Perhaps we should split the *.keep flag into two things or
>     more.
> 
>     We're using it for all of "I want this *.pack forever"
>     (e.g. debugging) and "I want only this *.pack to contain the data
>     found in it" (I/O & CPU optimization, what Janos wants) and "I'm
>     git.git code avoiding a race with myself" (what you describe in #3).
> 
>     So maybe for the last of those we could also use and understand
>     *.tmp-keep, at which point we wouldn't have this race described in
>     #3. The 1st of those is a *.noprune and the 2nd is *.highlander (but
>     whether it's worth splitting all that out v.s. just having
>     *.tmp-keep is another matter).