Make the value nil in text-quoting-style mean what it does in Emacs 25.

This is a partial reversion of yesterday's commit by the same author, which
changed the meaning of nil and introduced the new value t.

* src/doc.c (text_quoting_style, text-quoting-style)
(internal--text-quoting-flag): Revert yesterday's changes.

* lisp/cus-start.el: (top level): Amend the entry for text-quoting-style.

* etc/NEWS: Amend the entry for text-quoting-style.

* doc/lispref/control.texi (Signalling Errors)
* doc/lispref/display.texi (Displaying Messages)
* doc/lispref/strings.texi (Formatting Strings): Bind text-quoting-style to
grave rather than nil to inhibit translation of quotes.

* doc/lispref/help.texi (Keys in Documentation): Revert the description of the
proposed new default, t.

4 files changed, 11 insertions, 11 deletions

diff --git a/doc/lispref/control.texi b/doc/lispref/control.texi
index 09435f57966..c39e035459e 100644
--- a/doc/lispref/control.texi
+++ b/doc/lispref/control.texi
@@ -1109,7 +1109,7 @@ quotes.  In contrast, a call using a format like @t{"Missing '%s'"}
 with only apostrophes typically generates a message like @t{"Missing
 ’foo’"} with only closing curved quotes, an unusual style in English.
 One way around this problem is to bind @code{text-quoting-style} to
-@code{nil} around the call to @code{error}; this causes the
+the symbol @code{grave} around the call to @code{error}; this causes
 @acronym{ASCII} quote characters to be output unchanged.
 
 @strong{Warning:} If you want to use your own string as an error message
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 8f58fca506f..62b136f6c60 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -273,7 +273,7 @@ quotes.  In contrast, a call using a format like @t{"Missing '%s'"}
 with only apostrophes typically generates a message like @t{"Missing
 ’foo’"} with only closing curved quotes, an unusual style in English.
 One way around this problem is to bind @code{text-quoting-style} to
-@code{nil} around calls to @code{message}; this causes the
+the symbol @code{grave} around calls to @code{message}; this causes
 @acronym{ASCII} quote characters to be output unchanged.
 
 In batch mode, the message is printed to the standard error stream,
diff --git a/doc/lispref/help.texi b/doc/lispref/help.texi
index e1e98124e08..74dc6dac9cb 100644
--- a/doc/lispref/help.texi
+++ b/doc/lispref/help.texi
@@ -359,11 +359,11 @@ should use for single quotes in the wording of help and messages.  If
 the variable's value is @code{curve}, the style is @t{‘like this’}
 with curved single quotes.  If the value is @code{straight}, the style
 is @t{'like this'} with straight apostrophes.  If the value is
-@code{nil} or @code{grave}, quotes are not translated and the style is
-@t{`like this'} with grave accent and apostrophe, the standard style
-before Emacs version 25.  The default value @code{t} acts like
-@code{curve} if curved single quotes seem to be displayable, and like
-@code{nil} otherwise.
+@code{grave}, quotes are not translated and the style is @t{`like
+this'} with grave accent and apostrophe, the standard style before
+Emacs version 25.  The default value @code{nil} acts like @code{curve}
+if curved single quotes seem to be displayable, and like @code{grave}
+otherwise.
 
 This option is useful on platforms that have problems with curved
 quotes.  You can customize it freely according to your personal
diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 117a373a190..10385e05501 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -836,10 +836,10 @@ this'} typically generates curved quotes @t{‘like this’}.  In
 contrast, a format that quotes with only apostrophes @t{'like this'}
 typically generates two closing curved quotes @t{’like this’}, an
 unusual style in English.  One way around such problems is to bind
-@code{text-quoting-style} to @code{nil} around calls to
-@code{format-message}; this causes the @acronym{ASCII} quoting
-characters to be output unchanged.  @xref{Keys in Documentation}, for
-how the @code{text-quoting-style} variable affects generated quotes.
+@code{text-quoting-style} to the symbol @code{grave} around calls to
+@code{format-message}; this causes @acronym{ASCII} quoting characters
+to be output unchanged.  @xref{Keys in Documentation}, for how the
+@code{text-quoting-style} variable affects generated quotes.
 @end defun
 
 @cindex @samp{%} in format