feat: add option to keep HEAD on left

[mbtools]

Still work in progress

Summary of the issue

When displaying multiple branches, it's possible (for maintainers quite likely) that HEAD is not the most recent commit and the line representing the HEAD branch rendered somewhere in the middle of the branches.

Proposed solution

This PR adds a toggle setting show the HEAD branch always on the left. This allows easy identification of the HEAD branch by position. Since the position becomes stable, the HEAD branch will also maintain a stable color.

Setting: git-graph.repository.commits.headOnLeft: boolean, default false

Demo

If the setting is active, the graph adjusts automatically when a different branch is checked out moving the checked out branch to the left (it's a big repo and my system is a bit slow).

Note

Implemented with help from Cursor Composer.

[hansu]

Nice feature 👍
Let me now if you are done with this.

[mbtools]

There's still some glitch. I thought is was easier but working on it.

[hansu]

Yeah for my first test it didn't work as expected.

[mbtools]

It's working well now for me. I added a demo above. please give it a try.

[hansu]

Works ok but one little comment.

Given this example

With headOnLeft it also touches another line and it looks like the whole graph is mirrored:

Do you think you can tune that behaviour?

[mbtools]

Before: A checkout was treated as a swap: everything on head column traded places with everything on far left. The branch that was leftmost jumped to HEAD’s old column, so the whole column layout looked reshuffled.

Now: We move column from → to (from > to for headOnLeft): that column’s lines/dots/slots go to to, and every column index in [to, from) shifts right by 1. Relative order of the other tracks is unchanged; only HEAD’s track is pulled left through that range.

In your case above, blue and green branches should remain in the same order.

[hansu]

It looks now so in my example: