On Mar 25, 2014, at 6:17 PM, Junio C Hamano <gits...@pobox.com> wrote:
> Junio C Hamano <gits...@pobox.com> writes:
>> Ævar Arnfjörð Bjarmason <ava...@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.
That was actually one of my first ideas - adding some sort of '--auto-repack'
option to git-clone. It's a relatively small change, and would work. However,
keeping in mind my end goal of automating the feature to the point where you
could run simply 'git clone <url>', an '--auto-repack' option is more difficult
to undo. You would need a new parameter to disable the automatic adding of
reference repositories, and a new parameter to undo '--auto-repack', and you'd
have to remember to actually undo both of those settings.
In contrast, if the new feature was '--borrow', and the evolution of the
feature was a global configuration 'fetch.autoBorrow', then to turn it off
temporarily, one only needs a single new parameter '--no-auto-borrow'. I think
this is a cleaner approach than the former, although much more work.
- Andrew Keller
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