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Re: Storing refs in the odb

From
Johan Herland <johan@herland.net>
Date
May 20, 2013, 17:37 UTC
Message-ID
<CALKQrgdWx5mw3NCd4JOr3x9M34c2rNjm_tz_C7fm7g7g-LUJZQ@mail.gmail.com>
In-Reply-To
<7vbo85wos9.fsf@alter.siamese.dyndns.org>
On Mon, May 20, 2013 at 7:21 PM, Junio C Hamano <gitster@pobox.com> wrote:
Show 25 quoted lines
> Johan Herland <johan@herland.net> writes:
>
>>> Of course in either case we couldn't use a tree object directly, because
>>> these new "reference tree" objects would refer not only to blobs and
>>> other trees but also to commits and tags.
>>
>> Indeed. I don't know if the best solution would be to actually _allow_
>> that (which would complicate the object parsing code somewhat; a tree
>> entry pointing to a commit is usually interpreted as a submodule, but
>> that is not what we'd want for the ref tree, and a tree entry pointing
>> at a tag has AFAIK not yet been done), or whether it means we need to
>> come up with a different kind of structure.
>
> You can disallow that only by giving up on being able to express
> Linus's kernel repository, which has an oddball v2.6.11-tree tag.
>
> I do not think that that particular tag in the particular repository
> is too big a show-stopper; if it is only Linus, we can ask him to
> drop that tag (he has v2.6.11 tag object that points at the tree, so
> the users do not lose anything) and be done with it.
>
> But if there are other repositories that tag trees in a similar way,
> that would be a real regression.  We cannot just go ask people to
> change their workflow that depended on using refs that directly
> point at trees overnight.

I wasn't considering disallowing _anything_, rather open up to the idea that a tree object might refer to tag objects as well as commits/trees/blobs. E.g. in my suggested-but-pretty-much-retracted scheme, I was considering whether the tree entry at the "virtual" path "refs/tags/v1.0" should look like this:

  100644 blob 123456... v1.0

where the blob at 123456... contains the object id of the v1.0 tag object, or whether we should allow the crazyness that is:

  ?????? tag 987654... v1.0
Just a thought experiment...
...Johan
-- 
Johan Herland, <johan@herland.net>
www.herland.net
Previous: Junio C HamanoNext: Junio C Hamano
Message 3 of 5 in “Storing refs in the odb (was: Re: [PATCH 00/17] Remove assumptions about refname lifetimes)”
  1. Johan HerlandMay 20, 2013
  2. Junio C HamanoMay 20, 2013
  3. Johan HerlandMay 20, 2013
  4. Junio C HamanoMay 20, 2013
  5. Johan HerlandMay 20, 2013

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