vim-patch:d6c9ac9: runtime(doc): clarify the effect of 'smarttab'

closes: vim/vim#17426

d6c9ac97a0

Co-authored-by: Damien Lejay <damien@lejay.be>

src/nvim/options.lua

@@ -8182,16 +8182,11 @@ local options = {
       abbreviation = 'sta',
       defaults = true,
       desc = [=[
-        When on, a <Tab> in front of a line inserts blanks according to
-        'shiftwidth'.  'tabstop' or 'softtabstop' is used in other places.  A
-        <BS> will delete a 'shiftwidth' worth of space at the start of the
-        line.
-        When off, a <Tab> always inserts blanks according to 'tabstop' or
-        'softtabstop'.  'shiftwidth' is only used for shifting text left or
-        right |shift-left-right|.
-        What gets inserted (a <Tab> or spaces) depends on the 'expandtab'
-        option.  Also see |ins-expandtab|.  When 'expandtab' is not set, the
-        number of spaces is minimized by using <Tab>s.
+        When enabled, the <Tab> key will indent by 'shiftwidth' if the cursor
+        is in leading whitespace.  The <BS> key has the opposite effect.
+        This behaves as if 'softtabstop' is set to the value of 'shiftwidth'.
+        Have a look at section |30.5| of the user guide for detailed
+        explanations on how Vim works with tabs and spaces.
       ]=],
       full_name = 'smarttab',
       scope = { 'global' },