Re: [PATCH v3 4/8] rebase: store orig_head as a commit

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Junio

On 13/10/2022 17:34, Junio C Hamano wrote:
> "Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> To avoid changing the behavior of "git rebase <upstream> <branch>" we
>> keep the existing call to read_ref() and use lookup_commit_reference()
>> on the oid returned by that rather than calling
>> lookup_commit_reference_by_name() which applies the ref dwim rules to
>> its argument.
> 
> I agree with the above in that _by_name was an overly broad and
> wrong function to call.  But ...
> 
>> lookup_commit_reference() will dereference tag objects
>> but we do not expect the branch being rebased to be pointing to a tag
>> object.
> 
> ... if we do not expect to see a tag object, why call _reference()
> in the first place?  Does lookup_commit() not work for the purpose
> of this code?

I was wasn't convinced that the tag dereferencing was the only 
difference between lookup_commit_reference() and lookup_commit(). 
lookup_commit() calls lookup_object() and if the object is not in the 
parsed objects hash table it creates a new commit object with the given 
oid without checking if the object exists. lookup_commit_reference() 
calls parse_object() which handles replacement objects and checks the 
object actually exists.

Best Wishes

Phillip