From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 25 Mar 2014 22:17:07 GMT
Subject: Re: Borrowing objects from nearby repositories
Message-ID: <xmqqvbv1kjoc.fsf@gitster.dls.corp.google.com>
In-Reply-To: <xmqqtxammctc.fsf@gitster.dls.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>>> 1) Introduce '--borrow' to `git-fetch`.  This would behave similarly
>> to '--reference', except that it operates on a temporary basis, and
>> does not assume that the reference repository will exist after the
>> operation completes, so any used objects are copied into the local
>> objects database.  In theory, this mechanism would be distinct from
>> --reference', so if both are used, some objects would be copied, and
>> some objects would be accessible via a reference repository referenced
>> by the alternates file.
>>
>> Isn't this the same as git clone --reference <path> --no-hardlinks
>> <url> ?
>>
>> Also without --no-hardlinks we're not assuming that the other repo
>> doesn't go away (you could rm-rf it), just that the files won't be
>> *modified*, which Git won't do, but you could manually do with other
>> tools, so the default is to hardlink.
>
> I think that the standard practice with the existing toolset is to
> clone with reference and then repack.  That is:
>
>     $ git clone --reference <borrowee> git://over/there mine
>     $ cd mine
>     $ git repack -a -d
>
> And then you can try this:
>
>     $ mv .git/objects/info/alternates .git/objects/info/alternates.disabled
>     $ git fsck
>
> to make sure that you are no longer borrowing anything from the
> borrowee.  Once you are satisfied, you can remove the saved-away
> alternates.disabled file.

Oh, I forgot to say that I am not opposed if somebody wants to teach
"git clone" a new option to copy its objects from two places,
(hopefully) the majority from near-by reference repository and the
remainder over the network, without permanently relying on the
former via the alternates mechanism.  The implementation of such a
feature could even literally be "clone with reference first and then
repack" at least initially but even in the final version.