modechange: add notations +40, 00440, etc.
* lib/modechange.c (mode_compile): Support new notations
+40, -40, =440, 00440.  See <http://debbugs.gnu.org/8391>.
diff --git a/lib/modechange.c b/lib/modechange.c
index 4ae90ca..ea46b6c 100644
--- a/lib/modechange.c
+++ b/lib/modechange.c
@@ -136,6 +136,7 @@ mode_compile (char const *mode_string)
   /* The array of mode-change directives to be returned.  */
   struct mode_change *mc;
   size_t used = 0;
+  char const *p;

   if ('0' <= *mode_string && *mode_string < '8')
     {
@@ -143,40 +144,43 @@ mode_compile (char const *mode_string)
       mode_t mode;
       mode_t mentioned;

+      p = mode_string;
       do
         {
-          octal_mode = 8 * octal_mode + *mode_string++ - '0';
+          octal_mode = 8 * octal_mode + *p++ - '0';
           if (ALLM < octal_mode)
             return NULL;
         }
-      while ('0' <= *mode_string && *mode_string < '8');
+      while ('0' <= *p && *p < '8');

-      if (*mode_string)
+      if (*p)
         return NULL;

       mode = octal_to_mode (octal_mode);
-      mentioned = (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO;
+      mentioned = (p - mode_string < 5
+                   ? (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO
+                   : CHMOD_MODE_BITS);
       return make_node_op_equals (mode, mentioned);
     }

   /* Allocate enough space to hold the result.  */
   {
     size_t needed = 1;
-    char const *p;
     for (p = mode_string; *p; p++)
       needed += (*p == '=' || *p == '+' || *p == '-');
     mc = xnmalloc (needed, sizeof *mc);
   }

-  /* One loop iteration for each '[ugoa]*([-+=]([rwxXst]*|[ugo]))+'.  */
-  for (;; mode_string++)
+  /* One loop iteration for each
+     '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.  */
+  for (p = mode_string; ; p++)
     {
       /* Which bits in the mode are operated on.  */
       mode_t affected = 0;

       /* Turn on all the bits in 'affected' for each group given.  */
-      for (;; mode_string++)
-        switch (*mode_string)
+      for (;; p++)
+        switch (*p)
           {
           default:
             goto invalid;
@@ -199,35 +203,59 @@ mode_compile (char const *mode_string)

       do
         {
-          char op = *mode_string++;
+          char op = *p++;
           mode_t value;
           char flag = MODE_COPY_EXISTING;
           struct mode_change *change;

-          switch (*mode_string++)
+          switch (*p)
             {
+            case '0': case '1': case '2': case '3':
+            case '4': case '5': case '6': case '7':
+              {
+                unsigned int octal_mode = 0;
+
+                do
+                  {
+                    octal_mode = 8 * octal_mode + *p++ - '0';
+                    if (ALLM < octal_mode)
+                      return NULL;
+                  }
+                while ('0' <= *p && *p < '8');
+
+                if (affected || (*p && *p != ','))
+                  return NULL;
+                affected = CHMOD_MODE_BITS;
+                value = octal_to_mode (octal_mode);
+                flag = MODE_ORDINARY_CHANGE;
+                break;
+              }
+
             case 'u':
               /* Set the affected bits to the value of the "u" bits
                  on the same file.  */
               value = S_IRWXU;
+              p++;
               break;
             case 'g':
               /* Set the affected bits to the value of the "g" bits
                  on the same file.  */
               value = S_IRWXG;
+              p++;
               break;
             case 'o':
               /* Set the affected bits to the value of the "o" bits
                  on the same file.  */
               value = S_IRWXO;
+              p++;
               break;

             default:
               value = 0;
               flag = MODE_ORDINARY_CHANGE;

-              for (mode_string--;; mode_string++)
-                switch (*mode_string)
+              for (;; p++)
+                switch (*p)
                   {
                   case 'r':
                     value |= S_IRUSR | S_IRGRP | S_IROTH;
@@ -262,14 +290,13 @@ mode_compile (char const *mode_string)
           change->value = value;
           change->mentioned = (affected ? affected & value : value);
         }
-      while (*mode_string == '=' || *mode_string == '+'
-             || *mode_string == '-');
+      while (*p == '=' || *p == '+' || *p == '-');

-      if (*mode_string != ',')
+      if (*p != ',')
         break;
     }

-  if (*mode_string == 0)
+  if (*p == 0)
     {
       mc[used].flag = MODE_DONE;
       return mc;