From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Wed, 31 Aug 2011 01:35:02 GMT
Subject: Re: [PATCH 1/3] traverse_trees(): allow pruning with pathspec
Message-ID: <CACsJy8BsnKQx2Z1bs3Sdx-1ROeFvCZQkwQT8bWnyzL9du-T3Fw@mail.gmail.com>
In-Reply-To: <7v39gi3ib6.fsf@alter.siamese.dyndns.org>

On Wed, Aug 31, 2011 at 12:44 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Nguyen Thai Ngoc Duy <pclouds@gmail.com> writes:
>
>>> @@ -376,16 +396,22 @@ int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
>>>                        mask |= 1ul << i;
>>>                        if (S_ISDIR(entry[i].mode))
>>>                                dirmask |= 1ul << i;
>>> +                       e = &entry[i];
>>>                }
>>
>> Why? "e" is not used in that loop or anywhere after that.
>
> This is trying to find _a_ surviving entry to be fed to prune_traversal()
> which in turn uses tree_entry_interesting(). At this point in the code, we
> are stuffing the entries of the same name from the input trees (and if one
> tree is missing an entry of the chosen name, it will have NULL there), so
> any non-empty entry would do. It corresponds to "first" but that is just a
> simple string and not a name_entry tree_entry_interesting() wants.

Ah yes. I only searched in old code, "e" is used in the new
prune_traversal() call.

>>>                if (!mask)
>>>                        break;
>>> -               ret = info->fn(n, mask, dirmask, entry, info);
>>> -               if (ret < 0) {
>>> -                       error = ret;
>>> -                       if (!info->show_all_errors)
>>> -                               break;
>>> +               interesting = prune_traversal(e, info, &base, interesting);
>>> +               if (interesting < 0)
>>> +                       break;
>>
>> I don't really understand this function to comment. But I guess when
>> interesting < 0, we only skip info->fn() and assume it returns "mask"
>> (its user unpack_callback() only returns either "mask" or -1).
>
> We consume the entries we have used in merging (which is actually
> "everything in entry[] array" as info->fn() returns "mask" itself) by
> saying "update_extended_entry()" and the purpose of doing so is to prepare
> to process the next entry of the tree we are traversing.
>
> When tree_entry_interesting() returns negative, it tells us "no, and no
> subsequent entries will be either", meaning "we are done with this tree".
> As we are done, there is nothing to prepare for the next round; we are not
> walking the remaining entries in the trees we are looking at. Is there any
> point in calling update_extended_entry() I am missing?

No you're right again. Somehow I thought there would be another round
in the loop (ie. continue, not break). My bad.
-- 
Duy