Re: diff-index --cc no longer permitted, gitk is now broken (slightly)

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 30, 2021, 17:12 UTC
Message-ID: <xmqqsfyq501v.fsf@gitster.g>
In-Reply-To: <e6bd4cf7-ec8b-5d22-70f6-07089794df0c@kdbg.org>

Johannes Sixt <j6t@kdbg.org> writes:

Show 15 quoted lines

> Since 19b2517f95a0 (diff-merges: move specific diff-index "-m" handling
> to diff-index, 2021-05-21) git diff-index no longer accepts --cc. This
> breaks gitk: it invokes
>
>    git diff-index --cached -p -C --cc --no-commit-id -U3 HEAD
>
> to show the staged changes (when the line "Local changes checked in to
> index but not committed" is selected).
>
> The man page of git diff-index does not mention --cc as an option. I
> haven't fully grokked the meaning of --cc, so I cannot tell whether this
> absence has any significance (is deliberate or an omission).
>
> Is gitk wrong to add --cc unconditionally? Should it do so only when
> there are conflicts? Or not at all?

I think --cc is designed to naturally fall back to -p when there is only one parent. Use of both -p and --cc has also long been an acceptable combination, and even if we say the later --cc overrides -p, there is no reason not to show single parent patch here with --cc.