From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Mon, 02 Apr 2012 01:00:22 GMT
Subject: Re: GSoC - Some questions on the idea of
Message-ID: <CACsJy8CJK4gZwnrqkhq2DUqErS94X=99kvB9z=x9TefG=MrE4A@mail.gmail.com>
In-Reply-To: <CA+M5ThTnd+TST6WsAn-Jd=Gb=1EWaJ+QbLMxXgtAVFNVqnRcMw@mail.gmail.com>

On Mon, Apr 2, 2012 at 6:30 AM, Bo Chen <chen@chenirvine.org> wrote:
> One question,  can anyone help me clear?
>
> My .git/objects has 3 blobs, a, b, and c. a is a unique file, b and c
> two sequential versions of the same file. When I run "git gc", what
> exactly happens here, e.g., how exactly git (in the latest version)
> delta compresses-the blobs here?

See Documentation/technical/pack-heuristics.txt for how pack-objects
(called by"git gc") decides to delta either b or c based on the other
one. Once it chooses, say, b to be delta against c, it generates delta
using diff-delta.c, then store the delta in either ref-delta or
ofs-delta format. The former stores sha-1 of c, the latter the offset
of c in the pack.
-- 
Duy