Re: pack v4 trees with a canonical base

From: Nicolas Pitre <nico@fluxnic.net>
Date: Sep 10, 2013, 20:17 UTC
Message-ID: <alpine.LFD.2.03.1309101615080.20709@syhkavp.arg>
In-Reply-To: <xmqqbo40xwnv.fsf@gitster.dls.corp.google.com>

On Tue, 10 Sep 2013, Junio C Hamano wrote:

Show 18 quoted lines

> Duy Nguyen <pclouds@gmail.com> writes:
> 
> > On Tue, Sep 10, 2013 at 2:25 AM, Nicolas Pitre <nico@fluxnic.net> wrote:
> >> An eventual optimization to index-pack when completing a pack would be
> >> to attempt the encoding of appended tree objects into the packv4 format
> >> using the existing dictionary table in the pack, and fall back to the
> >> canonical format if that table doesn't have all the necessary elements.
> >
> > Yeah, it's on the improvement todo list. The way pack-objects creates
> > dictionaries right now, the tree dict should contain all elements the
> > base trees need so fall back is only necessary when trees are have
> > extra zeros in mode field.
> 
> Careful.
> 
> There may be trees in the wild that record 100775 or 100777 in the
> mode field for executable blobs, which also need to be special
> cased.

All the file mode bits are always preserved. So this is not really a special case as far as the pack v4 encoding is concerned.

Nicolas