Re: [PATCH v3 08/13] graph: tidy up display of left-skewed merges

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 16, 2019, 04:00 UTC
Message-ID: <xmqqsgnt8hlh.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <c34a5eb160310613cbde6313cda6cff753d6d7fd.1571183279.git.gitgitgadget@gmail.com>

"James Coglan via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 12 quoted lines

> This effect is applied to both "normal" two-parent merges, and to
> octopus merges. It also reduces the vertical space needed for pre-commit
> lines, as the merge occupies one less column than usual.
>
>         Before:         After:
>
>         | *             | *
>         | |\            | |\
>         | | \           | * \
>         | |  \          |/|\ \
>         | *-. \
>         | |\ \ \

Looking at these drawings reminded me of a tangent that is brought up from time to time. We do not do great job when showing multiple roots.

If you have a history like this:

      A---D---E
         /
    B---C

drawing the graph _with_ the merge gives a reasonable representation of the entire topology.

    * 46f67dd E
    *   6f89516 D
    |\  
    | * e6277a9 C
    | * 13ae9b2 B
    * afee005 A

But if you start drawing from parents of D (excluding D), you'd get this:

    * e6277a9 C
    * 13ae9b2 B
    * afee005 A

and the fact that B and A do not share parent-child relationships is lost. An easy way to show that would be to draw the bottom three lines of the full history output we saw earlier:

    | * e6277a9 C
    | * 13ae9b2 B
    * afee005 A

either with or without the vertical bar to imply that A may have a child.

This is not something that has to be done as part of this series, but I am hoping that the internal simplification and code restructuring that is done by this series would make it easier to enhance the system to allow such an output.

Thanks.