Re: [PATCH v5 14/15] fast-export: make sure updated refs get updated

> When an object has already been exported (and thus is in the marks) it's
> flagged as SHOWN, so it will not be exported again, even if in a later
> time it's exported through a different ref.
> 
> We don't need the object to be exported again, but we want the ref
> updated, which doesn't happen.
> 
> Since we can't know if a ref was exported or not, let's just assume that
> if the commit was marked (flags & SHOWN), the user still wants the ref
> updated.
> 
> IOW: If it's specified in the command line, it will get updated,
> regardless of wihether or not the object was marked.

> 
> So:
> 
> % git branch test master
> % git fast-export $mark_flags master
> % git fast-export $mark_flags test
> 
> Would export 'test' properly.
> 
> Additionally, this fixes issues with remote helpers; now they can push
> refs wich objects have already been exported, and a few other issues as