Re: [PATCH RFC] parse_object: pass on the original sha1, not the replaced one

[Nguyen Thai Ngoc Duy <pclouds@gmail.com>]

On Fri, Aug 13, 2010 at 1:59 PM, Christian Couder
<chriscool@tuxfamily.org> wrote:
> On Saturday 07 August 2010 06:03:05 Nguyen Thai Ngoc Duy wrote:
>> On Thu, Aug 5, 2010 at 9:41 PM, Christian Couder
>>
>> <chriscool@tuxfamily.org> wrote:
>> > It looks like parse_commit() is buggy regarding replaced objects. But I
>> > am not sure how it should be fixed.
>>
>> It could be fixed the same way you did with parse_object(): replace
>> read_sha1_file() with read_sha1_file_repl(). You would also need to
>> fix parse_tree() and parse_tag(). But..
>>
>> > Anyway if you use parse_object(), then you don't need parse_commit(). So
>> > if possible you should use parse_object() instead of both
>> > lookup_commit() and parse_commit().
>>
>> That's how those functions are used. For example, in
>> traverse_commit_list(), lookup_*() may be called and uninteresting
>> objects marked UNINTERESTING. Later on in process_{tree,blob,tag},
>> parse_* may be called if their content is interesting.
>>
>> To me, the fix above will leave a gap when object->sha1 is the
>> original sha1, until parse_*() is called. It just does not sound good.
>
> What do you think about adding a parse_commit_repl() function like the patch
> below and then using it instead of parse_commit()?

How do you plan to use this new function? #define parse_commit(c)
parse_commit_repl(c) or use the new function explictly when needed?

You are going to need parse_tree_repl() too unless you declare
tree/blob replacement is not supported and make git-replace refuse
blob/tree replacement.

Another thing to address is, there will be a duration between
lookup_commit() and parse_commit_repl(), where object.sha1 is the
original one. If it is saved elsewhere, troubles are ahead.

> ------- >8 ---------------------------------------------------
>
> diff --git a/commit.c b/commit.c
> index 652c1ba..183a735 100644
> --- a/commit.c
> +++ b/commit.c
> @@ -316,6 +316,50 @@ int parse_commit(struct commit *item)
>        return ret;
>  }
>
> +int parse_commit_repl(struct commit **commit)
> +{
> +       enum object_type type;
> +       void *buffer;
> +       unsigned long size;
> +       int ret;
> +       const unsigned char *repl;
> +       struct commit *item = *commit;
> +
> +       if (!item)
> +               return -1;
> +       if (item->object.parsed)
> +               return 0;
> +       buffer = read_sha1_file_repl(item->object.sha1, &type, &size, &repl);
> +       if (!buffer)
> +               return error("Could not read %s",
> +                            sha1_to_hex(item->object.sha1));
> +
> +       if (item->object.sha1 != repl) {
> +               struct commit *repl_item = lookup_commit(repl);
> +               if (!repl_item) {
> +                       free(buffer);
> +                       return error("Bad replacement %s for commit %s",
> +                                    sha1_to_hex(repl),
> +                                    sha1_to_hex(item->object.sha1));
> +               }

You need to use lookup_object() instead here. lookup_commit() wil
create new object if "repl" is not found.
-- 
Duy