Re: [PATCH v5 03/19] builtin/diff-tree: convert to struct object_id

> On Wed, Feb 22, 2017 at 10:50:21AM -0800, Junio C Hamano wrote:
>
>> What the function does appears somewhat iffy in the modern world.
>> We are relying on the fact that while Git is operating in this mode
>> of reading a tuple of commits per line and doing log-tree, that Git
>> itself will not do the history traversal (instead, another instance
>> of Git that feeds us via our standard input is walking the history)
>> for this piece of code to work correctly.  
>> 
>> Of course, the "diff-tree --stdin" command was meant to sit on the
>> downstream of "rev-list --parents", so the assumption the code makes
>> (i.e. the parents field of the in-core commit objects do not have to
>> be usable for history traversal) may be reasonable, but still...
>
> I'm not sure it's that weird. "diff-tree" is about diffing, not
> traversal. The only reason it touches commit->parents at all (and
> doesn't just kick off a diff between the arguments it gets) is that it's
> been stuck with pretty-printing the commits, which might ask to show the
> parents.