Re: [PATCH 00/23] Preliminary pack v4 support

From: Nicolas Pitre <nico@fluxnic.net>
Date: Aug 28, 2013, 02:58 UTC
Message-ID: <alpine.LFD.2.03.1308272241470.14472@syhkavp.arg>
In-Reply-To: <CACsJy8AttNxePUG9cKw9ihAmRd=kFpcsgwe2yj_FRQbhc-akCg@mail.gmail.com>

On Wed, 28 Aug 2013, Duy Nguyen wrote:

Show 7 quoted lines

> On Tue, Aug 27, 2013 at 11:44 PM, Junio C Hamano <gitster@pobox.com> wrote:
> > As you have "0-index" escape hatch for SHA-1 table, but no similar
> > escape hatch for the people's name table, I can see why it may be
> > cumbersome to fix a thin pack by only appending to a received
> > packfile and updating a few header fields, though.
> 
> We also need an escape hatch for path name table.

Well, right. I think this is probably the cleanest solution if we don't want to update the commit/tree dictionary table with new entries (they could simply be appended at the end). That wouldn't work for the SHA1 table though, so perhaps a secondary table for the appended objects could then be carried into the pack index file.

> But what if we store
> appended objects in OBJ_REF_DELTA format where base ref is empty
> tree/commit and cached by sha1_file.c?

I don't follow you here. Missing objects need to be added to the pack, they can't be cached anywhere.

> We won't need to update
> dictionary tables. Parsing is a bit ugly though (e.g. v3 tree with v2
> base) but we have to deal with that anyway because people can have v2
> and v3 packs mixed in.

Absolutely.

Nicolas