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

[Junio C Hamano <gitster@pobox.com>]

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?

> 	Therefore [...]
>
> Better?
>
> Ciao,
> Johannes