I am an old user of 'tabbar-ruler' and friends from MELPA (https://melpa.org/#/tabbar-ruler) and have built your branch on Windows with the following results.

First, I tried this:

> 1. M-x tab-bar-mode RET
> 2. Click on the plus sign to create a new tab

I get the image tab-bar-mode.png (see tar-ball attached) and haven't understood much how to use it

> 3. Click on the previous tab
> 4. Click on the close icon
>

Then tried this, and the result is global-tab.png: notice, usually, Emacs here starts restoring about 65 buffers

> 1. M-x global-tab-line-mode
> 2. Click on the plus sign and select a buffer to create a new tab
> 3. Click on the previous tab
> 4. Click on the close icon
>

For comparison, with the same configuration (65 buffers) the result with tabbar-ruler from MELPA is tabbar-ruler.png: notice how the selected tab is highlighted compared to the others.

Tabbar-ruler allow for grouping per mode, see tabbar-ruler-permode.png.

Tanks for this work,
  Angelo.