Dennis Kaarsemaker <dennis@xxxxxxxxxxxxxxx> writes:
> On wo, 2015-12-30 at 13:20 -0800, Junio C Hamano wrote:
>> Dennis Kaarsemaker <dennis@xxxxxxxxxxxxxxx> writes:
>>
>> > diff --git a/reflog-walk.c b/reflog-walk.c
>> > index 85b8a54..b85c8e8 100644
>> > --- a/reflog-walk.c
>> > +++ b/reflog-walk.c
>> > @@ -236,8 +236,8 @@ void fake_reflog_parent(struct reflog_walk_info
>> > *info, struct commit *commit)
>> > reflog = &commit_reflog->reflogs->items[commit_reflog
>> > ->recno];
>> > info->last_commit_reflog = commit_reflog;
>> > commit_reflog->recno--;
>> > - commit_info->commit = (struct commit *)parse_object(reflog
>> > ->osha1);
>> > - if (!commit_info->commit) {
>> > + commit_info->commit = lookup_commit(reflog->osha1);
>> > + if (!commit_info->commit || parse_commit(commit_info
>> > ->commit)) {
>> > commit->parents = NULL;
>> > return;
>>
>> This looks somewhat roundabout and illogical. The original was bad
>> because it blindly assumed reflgo->osha1 refers to a commit without
>> making sure that assumption holds. Calling lookup_commit() blindly
>> is not much better, even though you are helped that the function
>> happens not to barf if the given object is not a commit.
>>
>> Also this changes semantics, no? Trace the original flow and think
>> what happens, when we see a commit object that cannot be parsed in
>> parse_commit_buffer(). parse_object() calls parse_object_buffer()
>> which in turn calls parse_commit_buffer() and the entire callchain
>> returns NULL. commit_info->commit will become NULL in such a case.
>>
>> With your code, lookup_commit() will store a non NULL in
>> commit_info->commit, and parse_commit() calls parse_commit_buffer()
>> and that would fail, so you clear commit->parents to NULL but fail
>> to set commit_info->commit to NULL.
>>
>> Why not keep the parse_object() as-is and make sure we error out
>> unless the result is a commit with a more explicit check, perhaps
>> like this, instead?
>
> lookup_commit actually returns NULL (via object_as_type) for objects
> that are not commits, so I don't think the above is true.
I think you did not read what you are responding to. I was talking
about the error case where the object _is_ a commit (hence lookup
returns it), but parse_commit_buffer() does not like its contents.
> The code below also loses the diagnostic message about the object
> not being a commit.
Giving such a diagnostic message is a BUG.
A ref can legitimately point at any type of object (only refs under
refs/heads/, aka "branches", must point at commits), so you MUST NOT
complain about seeing a non-commit in a reflog in general.
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