Add command to display full path of current file, even in distraction-free and full-screen modes

It would be very useful to have a command that displays the name and full path of the current file in the status bar, as vi does when Ctrl-G is pressed in command mode.  If the path is too long to fit in the status bar, the status bar should be temporarily enlarged to hold it, just as vi does for long paths.  If temporary resizing of the status bar is not possible, the command could display the path in the same sort of window used by search and replace, with the window disappearing when Esc is pressed.

Isn't this redundant?

No.  I know that the file name and path are displayed in the main window title bar and the tab title bar, but these are not always visible.  In full-screen mode, the window title bar is hidden, and the tab title bars are usually too small to show the full path of the current file, or even the complete file name.  In distraction-free mode, neither the window title bar nor the tabs are visible.