bug#51247: 28.0.60; Insufficient documentation of tab-bar.el internal functions

[Juri Linkov]

>> This text is still wrong:
>>
>>   Adding a function to the list causes the tab bar to show
>>   that string, or display a menu with those menu items when
>>   you click on the tab bar.
>>
>> The tab called "Menu" displays menu items from the global menu-bar,
>> not from those menu items mentioned in the doc string.
>> Those menu items are used only to display tabs.
>
> Then please point me to a function out of those mentioned in
> tab-bar-format's :options that returns a list of menu items.  The
> sentence in the doc string "Every item in the list is a function that
> returns a string, or a list of menu-item elements, or nil" wasn't
> mine, it was yours.  What did you have in mind when you wrote that?

- tab-bar-format-menu-global returns a list of menu items
  that display the "Menu" tab.  This tab is bound to a command
  that uses popup-menu to display the global menu on clicking.

- tab-bar-format-history returns a list of menu items
  that produce back and forward buttons.

- tab-bar-format-tabs and tab-bar-format-tabs-groups
  return a list of menu items that produce the tabs for the tab bar.
...

- Only tab-bar-separator returns a string.