Re: What's cooking in git.git (Jan 2009, #05; Wed, 21)

[Jeff King <peff@peff.net>]

On Sat, Jan 31, 2009 at 07:45:54PM +1300, Sam Vilain wrote:

> Is there any reason why the split has to be cast in stone at all?
> 
> ie, the code could just scan the root tree of the branch, and
> progressively descend into sub-trees based on a partial match of the
> object for which the note is to be found.  If you find a partial name
> then you expect that it is a tree and descend into it and scan for the
> rest.  If you find a complete name then you expect that it is a blob and
> open it.  If it turns out to be a tree then there are multiple notes for
> that commit.  Then I think you get the best of both worlds; you can
> start with a simple flat structure and then later someone can come along
> and make it split it when there are more than N entries in the root tree
> (where N is determined from profiling etc).

Actually, lookup is even easier than that: we iterate through the entire
tree recursively and add everything to a flat hash. So we really don't
care there what the layout is like (just take the first 40 characters of
any directory name as a hash).

But it violates the usual git principle of "content has a unique name".
What happens when I add "a/b" and you add "ab"? A dumb merge will let
both co-exist, but which one do you return for lookup?

> One would be to allow grafts to be noted.  These might want to live in a
> different place to refs/notes/commits, like refs/notes/grafts, to avoid
> performance issues and to recognise they are a different type of data.
> A second would be for commit header information - particularly the
> author field and commit description - to be amended.  I think this all
> belongs under refs/notes/commits.  These are in essence, historical
> corrections that don't need to alter the tree.

I agree that there should be multiple note hierarchies, and multiple
keys within each hierarchy. I have posted some thoughts on that before
(and you should be able to find them searching for "notes" in the list
archive), but unfortunately I have not had time to sit down and really
work out a notes implementation that matches what I posted (which I
don't think is that far from Dscho's work in next).

And I think what you are proposing (here and in the rest of your
message) is that certain notes hierarchies may have particular formats
and semantics. And that sounds reasonable to me.

-Peff