Support octopus merges (i.e. more than 2 parents)

[mlange-42]

Currently, only two parrents are supported.

[eMPee584]

mmh 🤔 .. so what was the difficulty you came accross supporting these?

[carlobellettini]

only the first two branches are correctly connected, while the remaining branches are not shown as merged into the main graph. This results in an incomplete visualization of the expected merge structure

gitgraph one:

 ○<┐    9d3c65e (HEAD -> main) Merge branches 'A', 'B' and 'C'
 ● │    a7bfc3b (A) AA
 │ │ ●  fbef574 (C) D
 │ │ ●  5e99f7a C
 │ ● │  d5b4a12 (B) B
 ├─┴─┘  
 ●      31ebe88 A

fbef574 is not connected

here the correct one:

*-.   [04 09:24.48] | Merge branches 'A', 'B' and 'C'    (HEAD -> main)
|\ \  
| | * [04 09:22.39] | D    (C)
| | * [04 09:22.27] | C   
| * | [04 09:22.15] | B    (B)
| |/  
* / [04 09:24.24] | AA    (A)
|/  
* [04 09:21.18] | A