Show a tooltip on mouse cursor hovering over ellipsized (shortened) pathbar breadcrumb buttons
Nautilus shortens long folder names in the pathbar, as you can see with "dossier de ..." in this screenshot:
However, when you put the mouse cursor over it, it should show a GtkTooltip to reveal the full name of that folder, as it is otherwise not possible to know it without switching folders and losing your context.
This would probably be a good "newcomer" bug to fix ;)