Re: [PATCH] Remove branch by putting a null sha1 into the ref file.

[Christian Couder <chriscool@tuxfamily.org>]

Junio C Hamano wrote:
> Linus Torvalds <torvalds@osdl.org> writes:
> > It's entirely possible that the proper way to do branch deletion with
> > packed branches is to simply re-pack without the old branch, rather
> > than the negative branch model. I couldn't really decide.
>
> After playing with branch deletion issues for some time, I
> started to think it would be a lot simpler if we do not mark
> a deleted branch with 0{40}.

I also came to the same conclusion and I wonder if we could delete a branch 
by moving the file ".git/refs/heads/frotz" 
to ".git/deleted-refs/heads/frotz".
If the branch is packed we could perhaps just create 
".git/deleted-refs/heads/frotz". 

It means everytime we are looking up a ref we have to check 
in ".git/deleted-refs/" first to see if it exists.

> But the latter falls apart if we use 0{40} convention to mark a
> deleted branch. Removing .git/refs/heads/frotz/nitfol file which
> has 0{40} and creating .git/refs/heads/frotz file resurrects
> frotz/nitfol branch that is still packed.

If we move ".git/refs/heads/frotz/nitfol" 
to ".git/deleted-refs/heads/frotz/nitfol" when we remove this ref, we only 
need to try to rmdir all subdirectories under ".git/refs/heads/frotz/" and 
then ".git/refs/heads/frotz/" to see if we can 
create ".git/refs/heads/frotz", and if we can, we won't 
resurect "frotz/nitfol" because ".git/deleted-refs/heads/frotz/nitfol" 
still exists.

> Not allowing frotz 
> branch to be created only because we had deleted frotz/nitfol
> previously is not what we want either, so at that point we need
> to repack without frotz/nitfol anyway.
>
> Which makes me think that we would better repack when removing
> any existing ref.

Yes but it may not be fast and may be corruption prone.

Christian.