Re: [PATCH] git clone depth of 0 not possible.

From: Junio C Hamano <gitster@pobox.com>
Date: May 28, 2013, 17:04 UTC
Message-ID: <7va9nf2fyp.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20130528091812.GG25742@login.drsnuggles.stderr.nl>

Matthijs Kooijman <matthijs@stdin.nl> writes:

Show 11 quoted lines

> Did you consider how to implement this? Looking at the code, it seems
> the "deepen" parameter in the wire protocol now means:
>  - 0: Do not change anything about the shallowness (i.e., fetch
>    everything from the shallow root to the tip).
>  - > 0: Create new shallow commits at depth commits below the tip (so
>    depth == 1 means tip and one below).
>  - INFINITE_DEPTH (0x7fffffff): Remove all shallowness and fetch
>    complete history.
>
> Given this, I'm not sure how one can express "fetch the tip and nothing
> below that", since depth == 0 already has a different meaning.

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.

In the longer term, I think we should introduce a better deepening mechanism. Cf.

  http://thread.gmane.org/gmane.comp.version-control.git/212912/focus=212940

> Of course, one could using depth == 1 in this case to receive two
> commits and then drop one, but this would seem a bit pointless to me
> (especially if the commit below the tip is very different from the tip
> leading to a lot of useless data transfer).