Re: [PATCH 06/11] graph: tidy up display of left-skewed merges

[Derrick Stolee <stolee@gmail.com>]

On 10/10/2019 12:13 PM, James Coglan via GitGitGadget wrote:
> From: James Coglan <jcoglan@gmail.com>
> 
> Currently, when we display a merge whose first parent is already present
> in a column to the left of the merge commit, we display the first parent
> as a veritcal pipe `|` in the GRAPH_POST_MERGE line and then immediately
> enter the GRAPH_COLLAPSING state. The first-parent line tracks to the
> left and all the other parent lines follow it; this creates a "kink" in
> those lines:
> 
>         | *---.
>         | |\ \ \
>         |/ / / /
>         | | | *
> 
> This change tidies the display of such commits such that if the first
> parent appears to the left of the merge, we render it as a `/` and the
> second parent as a `|`. This reduces the horizontal and vertical space
> needed to render the merge, and makes the resulting lines easier to
> read.
> 
>         | *-.
>         |/|\ \
>         | | | *
> 
> If the first parent is separated from the merge by several columns, a
> horizontal line is drawn in a similar manner to how the GRAPH_COLLAPSING
> state displays the line.
> 
>         | | | *-.
>         | |_|/|\ \
>         |/| | | | *
> 
> 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:
> 
>         | *             | *
>         | |\            | |\
>         | | \           | * \
>         | |  \          |/|\ \
>         | *-. \
>         | |\ \ \
> 

Thank you for adding these careful diagrams both to the message
and the code. These concepts are hard to track without a visual
aid.

[snip]

> +++ b/t/t4215-log-skewed-merges.sh
> @@ -0,0 +1,42 @@
> +#!/bin/sh
> +
> +test_description='git log --graph of skewed merges'
> +
> +. ./test-lib.sh
> +
> +test_expect_success 'setup left-skewed merge' '


Could you skew this example to include a left-skewed octopus merge
(and use fewer Git processes) with the following:

	git checkout --orphan _a && test_commit A &&
	git switch -c _b _a && test_commit B &&
	git switch -c _c _a && test_commit C &&
	git switch -c _d _a && test_commit D &&	git switch -c _e _b && git merge --no-ff _c _d E &&
	git switch -c _f _a && git merge --no-ff _d -m F &&	git checkout _a && git merge --no-ff _b _c _e _f -m G
and I think the resulting output will be:

*-----.   G
|\ \ \ \
| | | | * F
| |_|_|/|
|/| | | |
| | | * | E
| |_|/|\|
|/| | | |
| | |/  * D
| |_|__/
|/| |
| | * C
| |/
|/|
| * B
|/
* A