Assertion in git log graphing

Hi,

The following git repository (https://github.com/brads55/git-testcase)
causes an assertion when running:

  $ git log --oneline --graph --all

  git-log: graph.c:1228: graph_output_collapsing_line: Assertion
`graph->mapping[i - 3] == target' failed.

The assertion seems to be caused by commit
0f0f389f12029b1c3745f8ed7aacfe6b2fc7a6cc. The graph structure of the
above repository is as follows (as produced by v2.24.1):

*   a0a130c Merge commit '8f076d8' into HEAD
|\
| | *   f0f3be5 Merge commit '1b4b8d0' into HEAD
| | |\
| | | * 1b4b8d0 6
| | * | 2c44f1b 2
| | | | *   dd068b4 Merge commit '8f076d8' into HEAD
| | | | |\
| |_|_|/ /
|/| | | /
| | |_|/
| |/| |
| * | | 8f076d8 5
| | |/
| |/|
* | | a261135 4
| |/
|/|
* | a267dd6 1
|/
* 68f4772 0

Regards,
Bradley Smith