Start redesign of gedit
Use auto in the setting for notebook tabs
Set "gedit" as title when no tabs
Use show-close-button property
Integrate sidebar insto titlebar
Remove title from sidebar
Mark headerbars as titlebars.

See that we need custom css to remove the extra borders we have now
Show the right title for the sidebar headerbar
Move save button to the right
Add get_gear_menu to window and menu extension points
quickopen: add/remove menuitem
quickopen: add accelerator