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From: Matthijs Kooijman <matthijs@stdin.nl>
To: Junio C Hamano <gitster@pobox.com>
Cc: Duy Nguyen <pclouds@gmail.com>,
	Jonathan Nieder <jrnieder@gmail.com>,
	Stefan Beller <stefanbeller@googlemail.com>,
	schlotter@users.sourceforge.net, Ralf.Wildenhues@gmx.de,
	git@vger.kernel.org
Subject: Re: [PATCH] git clone depth of 0 not possible.
Date: Tue, 9 Jul 2013 15:35:42 +0200	[thread overview]
Message-ID: <20130709133542.GJ10217@login.drsnuggles.stderr.nl> (raw)
In-Reply-To: <7va9nf2fyp.fsf@alter.siamese.dyndns.org>

Hi Junio,

> Doing it "correctly" (in the shorter term) would involve:
> 
>  - adding a capability on the sending side "fixed-off-by-one-depth"
>    to the protocol, and teaching the sending side to advertise the
>    capability;
>    
>  - teaching the requestor that got --depth=N from the end user to
>    pay attention to the new capability in such a way that:
> 
>    - when talking to an old sender (i.e. without the off-by-one
>      fix), send N-1 for N greater than 1.  Punt on N==1;
> 
>    - when talking to a fixed sender, ask to enable the capability,
>      and send N as is (including N==1).
> 
>  - teaching the sending side to see if the new behaviour to fix
>    off-by-one is asked by the requestor, and stop at the correct
>    number of commits, not oversending one more.  Otherwise retain
>    the old behaviour.

While implementing the above, I noticed my fix now introduced an
off-by-one error the other way. When investigating, I found this commit:

	commit 682c7d2f1a2d1a5443777237450505738af2ff1a
	Author: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
	Date:   Fri Jan 11 16:05:47 2013 +0700

	    upload-pack: fix off-by-one depth calculation in shallow clone

	    get_shallow_commits() is used to determine the cut points at a given
	    depth (i.e. the number of commits in a chain that the user likes to
	    get). However we count current depth up to the commit "commit" but we
	    do the cutting at its parents (i.e. current depth + 1). This makes
	    upload-pack always return one commit more than requested. This patch
	    fixes it.

	    Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
	    Signed-off-by: Junio C Hamano <gitster@pobox.com>

Which actually seems to fix the off-by-one bug that is described in this
thread, but without going through the hoops of preserving current
behaviour for older git versions (that is, it makes behaviour dependent
on server version instead of client version).

Does this mean the discussion in this thread is meaningless, or is that
commit not intended to be the final fix?

In any case, IIUC that particular patch makes a piece of the existing
code dead, which needs to be removed.

Gr.

Matthijs

  parent reply	other threads:[~2013-07-09 13:35 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-07 18:06 Stefan Beller
2013-01-07 18:06 ` [PATCH] Documentation on depth option in git clone Stefan Beller
2013-01-08  6:28 ` [PATCH] git clone depth of 0 not possible Jonathan Nieder
2013-01-08  6:54   ` Junio C Hamano
2013-01-08  7:36     ` Junio C Hamano
2013-01-08  8:19       ` Junio C Hamano
2013-01-08 14:28       ` Duy Nguyen
2013-01-08 14:32         ` Stefan Beller
2013-01-08 14:45           ` Duy Nguyen
2013-01-08 17:24           ` Junio C Hamano
2013-01-08  7:38     ` Duy Nguyen
2013-01-08  8:05       ` Junio C Hamano
2013-05-28  9:18         ` Matthijs Kooijman
2013-05-28 16:28           ` Jonathan Nieder
2013-05-28 16:31             ` Jonathan Nieder
2013-05-28 16:34             ` Matthijs Kooijman
2013-05-28 16:58               ` Jonathan Nieder
2013-05-28 17:04           ` Junio C Hamano
2013-05-30  8:23             ` Matthijs Kooijman
2013-06-02 19:14               ` Junio C Hamano
2013-07-09 13:35             ` Matthijs Kooijman [this message]
2013-07-11 10:57               ` Matthijs Kooijman
2013-07-11 11:25                 ` [PATCH 1/3] upload-pack: Remove a piece of dead code Matthijs Kooijman
2013-07-11 11:25                   ` [PATCH 2/3] upload-pack: Introduce new "fixed-off-by-one-depth" server feature Matthijs Kooijman
2013-07-11 11:25                   ` [PATCH 3/3] fetch-pack: Request fixed-off-by-one-depth when available Matthijs Kooijman
2013-07-11 12:08                   ` [PATCH 1/3] upload-pack: Remove a piece of dead code Duy Nguyen
2013-07-11 15:49                     ` Junio C Hamano
2013-01-08  7:33 ` [PATCH] git clone depth of 0 not possible Duy Nguyen
2013-01-08  7:37   ` Junio C Hamano

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