substitute-command-keys now curves quotes

So, for example, it turns "`abc'" into "‘abc’" (Bug#20385).
* doc/lispref/help.texi (Keys in Documentation):
* etc/NEWS: Document this.
* src/doc.c (Fsubstitute_command_keys): Implement it.

1 files changed, 33 insertions, 6 deletions

diff --git a/src/doc.c b/src/doc.c
index 8b18fb0a5a2..32d65563fd9 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -693,15 +693,21 @@ summary).
 
 Each substring of the form \\=\\<MAPVAR> specifies the use of MAPVAR
 as the keymap for future \\=\\[COMMAND] substrings.
-\\=\\= quotes the following character and is discarded;
-thus, \\=\\=\\=\\= puts \\=\\= into the output, and \\=\\=\\=\\[ puts \\=\\[ into the output.
+
+Each \\=` is replaced by ‘.  Each ' preceded by \\=` and without
+intervening ' is replaced by ’.
+
+\\=\\= quotes the following character and is discarded; thus,
+\\=\\=\\=\\= puts \\=\\= into the output, \\=\\=\\=\\[ puts \\=\\[ into the output, and
+\\=\\=\\=` puts \\=` into the output.
 
 Return the original STRING if no substitutions are made.
 Otherwise, return a new string.  */)
   (Lisp_Object string)
 {
   char *buf;
-  bool changed = 0;
+  bool changed = false;
+  bool in_quote = false;
   unsigned char *strp;
   char *bufp;
   ptrdiff_t idx;
@@ -734,6 +740,12 @@ Otherwise, return a new string.  */)
   keymap = Voverriding_local_map;
 
   bsize = SBYTES (string);
+
+  /* Add some room for expansion due to quote replacement.  */
+  enum { EXTRA_ROOM = 20 };
+  if (bsize <= STRING_BYTES_BOUND - EXTRA_ROOM)
+    bsize += EXTRA_ROOM;
+
   bufp = buf = xmalloc (bsize);
 
   strp = SDATA (string);
@@ -743,7 +755,7 @@ Otherwise, return a new string.  */)
         {
           /* \= quotes the next character;
              thus, to put in \[ without its special meaning, use \=\[.  */
-          changed = 1;
+          changed = true;
           strp += 2;
           if (multibyte)
             {
@@ -766,7 +778,6 @@ Otherwise, return a new string.  */)
           ptrdiff_t start_idx;
           bool follow_remap = 1;
 
-          changed = 1;
           strp += 2;            /* skip \[ */
           start = strp;
           start_idx = start - SDATA (string);
@@ -833,7 +844,6 @@ Otherwise, return a new string.  */)
           Lisp_Object earlier_maps;
           ptrdiff_t count = SPECPDL_INDEX ();
 
-          changed = 1;
           strp += 2;            /* skip \{ or \< */
           start = strp;
           start_idx = start - SDATA (string);
@@ -903,6 +913,7 @@ Otherwise, return a new string.  */)
           length = SCHARS (tem);
           length_byte = SBYTES (tem);
         subst:
+          changed = true;
           {
             ptrdiff_t offset = bufp - buf;
             if (STRING_BYTES_BOUND - length_byte < bsize)
@@ -916,6 +927,22 @@ Otherwise, return a new string.  */)
             strp = SDATA (string) + idx;
           }
         }
+      else if (strp[0] == '`')
+        {
+          in_quote = true;
+          start = (unsigned char *) "\xE2\x80\x98"; /* ‘ */
+        subst_quote:
+          length = 1;
+          length_byte = 3;
+          idx = strp - SDATA (string) + 1;
+          goto subst;
+        }
+      else if (strp[0] == '\'' && in_quote)
+        {
+          in_quote = false;
+          start = (unsigned char *) "\xE2\x80\x99"; /* ’ */
+          goto subst_quote;
+        }
       else if (! multibyte)             /* just copy other chars */
         *bufp++ = *strp++, nchars++;
       else