Re: Why can't I push from a shallow clone?

From: Philip Oakley <philipoakley@iee.org>
Date: Jul 26, 2013, 21:48 UTC
Message-ID: <34D78815D927482897856F1C5BB2D183@PhilipOakley>
In-Reply-To: <CANEZYrdR3xLRSQAo6rroN3TLv48HEKp4_t95WEf6rm8-+r+2tw@mail.gmail.com>

From: "Gulshan Singh" <gsingh2011@gmail.com>
Sent: Friday, July 26, 2013 8:12 PM

Show 22 quoted lines

> Hey Fredrick,
>
> It's good to know that work is being done on this. I still want to
> understand it though, so I guess I'll ask specific questions about
> Junio's response. He states,
>
> "If you cloned shallowly some time ago, worked without communicating
> with the other side while the other side progressed, AND if the other
> side's progress included a rewind & rebuild of the history, you would
> see a similar topology.
> The leftmost 'S' in the above picture might have been the tip of the
> branch when you shallowly cloned with depth 1, and since then the
> remote end may have discarded topmost three commits and have rebuilt
> its history that leads to the rightmost 'R'. In such a case pushing to
> the remote's HEAD will fail."
>
> So as an example, if you shallow clone a branch, then someone squashes
> the head commit and makes a new commit, you won't be able to push to
> HEAD because the parent has changed. But if someone does that, I don't
> think you would be able to push even if it was a full clone. That's
> why it's usually not a good idea to rebase shared branches. So did I
> misunderstand the scenario?

In your example you have a sucessful failure, that is, the shallow issue hasn't got in the way of the normal non-ff failure on push. (asuming the squash is an extra commit, not a re-written top commit, so at least you still have your common commit of your depth1 shallow clone)

For it to be a proper shallow failure the remote repo needs to be re-written sufficiently far back that your shallow clone has nothing in common with it. In such a case your DAG can't join onto the remote's DAG.

Show 30 quoted lines

>
>
> On Thu, Jul 25, 2013 at 11:55 PM, Fredrik Gustafsson <iveqy@iveqy.com> 
> wrote:
>> On Thu, Jul 25, 2013 at 07:33:16PM -0700, Gulshan Singh wrote:
>>> I've been trying to figure out why I can't push from a shallow clone
>>> (using --depth) to a repository. I've made simple examples where it
>>> works, but I've read that in doesn't work in every case. However, I
>>> can't come up with a case where it doesn't work. Googling gives this
>>> answer: 
>>> http://stackoverflow.com/questions/6900103/why-cant-i-push-from-a-shallow-clone,
>>> but I don't completely understand the explanation, so I was hoping
>>> someone could explain it.
>>
>> I can't explain it better than what Junio did in the link you just
>> provide. However there's ongoing work to allow shallow clones to be 
>> able
>> to push. You can read about it here:
>> http://thread.gmane.org/gmane.comp.version-control.git/230612/focus=230878
>> --
>> Med vänliga hälsningar
>> Fredrik Gustafsson
>> tel: 0733-608274
>> e-post: iveqy@iveqy.com
> -- 
> Gulshan Singh
> University of Michigan, Class of 2015
> College of Engineering, Computer Science Major
> gulshan@umich.edu | 248.961.6317
> Alternate E-mail: gsingh2011@gmail.com

-- Philip