Re: [PATCH v3 04/11] Prepare `paint_down_to_common()` for handling shallow commits

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>
>> 	Currently, that logic pretends that a commit whose parent
>> 	commit is missing is a root commit (and likewise merge commits
>> 	with missing parent commits are handled incorrectly, too).
>> 	However, for the purpose of `--update-shallow` that is exactly
>> 	what we need to do (and only then).
>
> I suspect that what made it harder to follow in the original
> construct is that we called the behaviour "incorrect" upfront and
> then come back with "that incorrectness is what we want".  I wonder
> if it makes it easier to follow by flipping them around.
>
>     For the purpose of `--update-shallow`, when some of the parent
>     commits of a commit are missing from the repository, we need to
>     treat as if the parents of the commit are only the ones that do
>     exist in the repository and these missing commits have no
>     ancestry relationship with it.  If all its parent commits are
>     missing, the commit needs to be treated as if it were a root
>     commit.
>
>     Add a flag to optionally ask for such a behaviour, while
>     detecting missing objects as a repository corruption error by
>     default ...
>
> or something?