Re: [gentoo-dev] RFC: git-r3, additional clone types

[Alex Xu]

On 24/02/14 04:00 PM, Michał Górny wrote:
> Dnia 2014-02-24, o godz. 21:13:15
> Peter Stuge <peter@×××××.se> napisał(a):
>
>> Michał Górny wrote:
>>> Shallow clone
>>> -------------
>>> - EGIT_COMMIT can only name tags (using a hash auto-forces higher mode),
>>
>> Hm, why is that? This seems like an unfortunate and inconvenient
>> limitation which might actually reduce usefulness of shallow mode
>> quite severely? :\
>
> Limitation of git design. You can only fetch remote refs, you can't
> fetch an arbitrary hash. And since we don't download the whole history,
> we can't use a hash that was past 'depth' of the branch/tag clone. So
> in order to use an arbitrary hash, we actually have to download
> the history.

Perhaps you could have EGIT_FETCH_REF and EGIT_CHECKOUT?

>>> - changing branches may be very inefficient (since it implies
>>>   re-fetching all objects implied by --depth 1),
>>
>> If it's the same local repo then at least in theory all existing
>> blobs and trees don't strictly need to be transfered, only unseen
>> ones and all the refs. But I'm not sure if git is so good at dealing
>> with this - I haven't looked at exactly how packs are structured.
>
> It's not good at all. In fact, if you try to update a shallow clone
> with 'git fetch --depth 1', it's going to refetch all the objects
> (while plain 'git fetch' only downloads new objects). It's just another
> limitation of protocol that we can't do much about.

Can't you use `git fetch` as usual to download old..new commits only?
This wouldn't help with switching branches though.

>> I would prefer if I needed to allow such mode upgrades explicitly.
>
> That sounds like a lot ebuilds failing, requesting you to explicitly
> change the mode. For example, all Google Code hosted repositories
> do not support shallow mode. Some projects may require single-branch
> mode to handle their 'git log' play.

Perhaps EGIT_CLONE_MODE could be a USE_EXPAND (yes, another one)?

>>> When mirror or single-branch mode is used on a shallow repository,
>>> the repository is still marked 'shallow' even if the full history is
>>> available. I don't know if this wouldn't break some of 'git foo' uses
>>> in the checkout but that probably can't be predicted. Moreover, I don't
>>> know if it is safe to remove 'shallow' after doing full-fetch in mirror
>>> mode.

git fetch --unshallow according to
https://stackoverflow.com/questions/6802145/convert-shallow-clone-to-full-clone