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

From: Matthijs Kooijman <matthijs@stdin.nl>
Date: May 30, 2013, 08:23 UTC
Message-ID: <20130530082322.GW25742@login.drsnuggles.stderr.nl>
In-Reply-To: <7va9nf2fyp.fsf@alter.siamese.dyndns.org>

Hi Junio,

On Tue, May 28, 2013 at 10:04:46AM -0700, Junio C Hamano wrote:

Show 15 quoted lines

> Matthijs Kooijman <matthijs@stdin.nl> writes:
> 
> > 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:

Given below suggestion, I take it you don't like what Jonathan proposed (changing the meaning of the deepen parameter in the protocol so that the server effectively decides how to interpret --depth)?

Show 8 quoted lines

>  - 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 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.

We can implement these two in current git already, since they only add to the protocol, not break it in an incompatible manner, right?

Show 8 quoted lines

>  - 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).

And these should wait for git2, since they change the meaning of the --depth parameter? Or is this change ok for current git as well?

What do you mean by "punt" exactly? Show an error to the user, saying only depth >= 2 is supported?

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

Even when there will be a better deepening mechanism, the above is still useful (passing --depth=1 serves to get just a single commit without history, which is a distinct usecase from deepening the history of an existing shallow repository). In other words, I think the "improved deepening" and "fixed depth" should be complementary features.

Gr.

Matthijs