[BUG] Tabs and mode/header/frame-title update

[Ingo Lohmar <ingo.lohmar@posteo.net>]

Tabs are working great, but here is one minor thing I stumbled about,
and that eventually led me to a bug:

1) The bug is: at the end of `tab-bar-rename-tab`, it should read

@@ -687,7 +687,7 @@ tab-bar-rename-tab
                          (funcall tab-bar-tab-name-function))))
     (setf (cdr (assq 'name tab-to-rename)) tab-new-name
           (cdr (assq 'explicit-name tab-to-rename)) tab-explicit-name)
-    (if (tab-bar-mode)
+    (if tab-bar-mode
         (force-mode-line-update)
       (message "Renamed tab to '%s'" tab-new-name))))
 
so as not to turn on `tab-bar-mode`, but only to check its status.

2) However, I use tabs w/o tab-bar-mode and only looked at the code
above because I wondered why my frame-title (where I put the current tab
info) was not reliably updated when, eg, adding a tab.

IMO, such an update is *especially* relevant when you use the functions
without `tab-bar-mode`.  But all calls to `force-mode-line-update` (at
the end of various interactive functions) are conditioned on
`tab-bar-mode`.

Since this is by no means a frequent operation, I strongly suggest
to update the modeline(/header/title) unconditionally.