Re: Reading commit objects

From: Shawn Pearce <spearce@spearce.org>
Date: May 22, 2013, 20:02 UTC
Message-ID: <CAJo=hJuO23YGMJV69WvdKweW7EYCYVE-f93w5a=+N2_xh_e1+A@mail.gmail.com>
In-Reply-To: <CABx5MBS9YgNmZD_tumMJ-MJVjHbRFCKbCjs9AZ347-OCwqO7qQ@mail.gmail.com>

On Wed, May 22, 2013 at 7:20 AM, Chico Sokol <chico.sokol@gmail.com> wrote:

> I'm not criticizing JGit, guys. It simply doesn't fit into our needs.
> We're not interested in mapping git commands in java and don't have
> the same RAM limitations.

I guess you aren't trying to process the WebKit or Linux kernel repositories. Or you can afford more RAM than I can[1]. :-)

[1] $DAY_JOB has lots of RAM.  Lots.

> Are you guys contributors of JGit?

Not really. I had nothing to do with JGit.  :-)

> Can you guys point me out to the
> code that unpacks git objects? The closest I could get was that class:
> https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/UnpackedObject.java

This class handles the loose object format in $GIT_DIR/objects, but does not handle objects contained in pack files. That is elsewhere, and well, more complex. Look at PackFile.java.

> It seems to be a standard and a non standard format of the packed
> object, as I read the comments of this method:
> https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/UnpackedObject.java#L272

There are two formats, the official format that is used, and an experimental format that was discarded but is still supported for legacy reasons.

Show 5 quoted lines

> I suspect that the default inflater class of java api expect the
> object to be in the standard format.
>
> What the following comment mean? What's the "Experimental pack-based"
> format? Is there any docs on the specs of that?

Read the code. This is the dead format that is no longer written, but is still supported.