common: Add a flag for left anchored substring match to recsel.

* common/recsel.c (struct recsel_expr_s): Add field lefta.
(recsel_parse_expr): Parse it.
(recsel_select): Implement selection.
--

This flags makes it for example easy to select keys last updated from
an ldap server:

  gpg --list-filter 'select=origin=ks && -^ url =~ ldap' \
       -k --with-key-origin

common/recsel.c

@@ -64,6 +64,7 @@ struct recsel_expr_s
   unsigned int not:1;   /* Negate operators. */
   unsigned int disjun:1;/* Start of a disjunction.  */
   unsigned int xcase:1; /* String match is case sensitive.  */
+  unsigned int lefta:1; /* String match is left anchored.  */
   const char *value;    /* (Points into NAME.)  */
   long numvalue;        /* strtol of VALUE.  */
   char name[1];         /* Name of the property.  */
@@ -140,6 +141,7 @@ find_next_lc (char *string)
  * Values for <flag> must be space separated and any of:
  *
  *   --  VALUE spans to the end of the expression.
+ *   -^  The substring match is left anchored.
  *   -c  The string match in this part is done case-sensitive.
  *   -t  Do not trim leading and trailing spaces from VALUE.
  *       Note that a space after <op> is here required.
@@ -176,6 +178,7 @@ recsel_parse_expr (recsel_expr_t *selector, const char *expression)
   int toend = 0;
   int xcase = 0;
   int notrim = 0;
+  int lefta = 0;
   int disjun = 0;
   char *next_lc = NULL;
 
@@ -206,6 +209,7 @@ recsel_parse_expr (recsel_expr_t *selector, const char *expression)
         case '-': toend = 1; break;
         case 'c': xcase = 1; break;
         case 't': notrim = 1; break;
+        case '^': lefta = 1; break;
         default:
           log_error ("invalid flag '-%c' in expression\n", *expr);
           recsel_release (se_head);
@@ -235,6 +239,7 @@ recsel_parse_expr (recsel_expr_t *selector, const char *expression)
   se->not = 0;
   se->disjun = disjun;
   se->xcase = xcase;
+  se->lefta = lefta;
 
   if (!se_head)
     se_head = se;
@@ -463,9 +468,10 @@ recsel_dump (recsel_expr_t selector)
   log_debug ("--- Begin selectors ---\n");
   for (se = selector; se; se = se->next)
     {
-      log_debug ("%s %s %s %s '%s'\n",
+      log_debug ("%s %s %s %s %s '%s'\n",
                  se==selector? "  ": (se->disjun? "||":"&&"),
                  se->xcase?  "-c":"  ",
+                 se->lefta?  "-^":"  ",
                  se->name,
                  se->op == SELECT_SAME?    (se->not? "<>":"= "):
                  se->op == SELECT_SUB?     (se->not? "!~":"=~"):
@@ -529,9 +535,15 @@ recsel_select (recsel_expr_t selector,
               break;
             case SELECT_SUB:
               if (se->xcase)
-                result = !!gnupg_memstr (value, valuelen, se->value);
+                result = (gnupg_memstr (value, valuelen, se->value)
+                          && (!se->lefta
+                              || (selen <= valuelen
+                                  && !memcmp (value, se->value, selen))));
               else
-                result = !!memistr (value, valuelen, se->value);
+                result = (memistr (value, valuelen, se->value)
+                          && (!se->lefta
+                              || (selen <= valuelen
+                                  && !memicmp (value, se->value, selen))));
               break;
             case SELECT_NONEMPTY:
               result = !!valuelen;

common/t-recsel.c

@@ -225,9 +225,27 @@ run_test_2 (void)
   if (!recsel_select (se, test_2_getval, NULL))
     fail (0, 0);
   FREEEXPR();
-  ADDEXPR ("uid =~ @");
+  ADDEXPR ("uid !~ @");
+  if (recsel_select (se, test_2_getval, NULL))
+    fail (0, 0);
+
+  FREEEXPR();
+  ADDEXPR ("uid =~ foo@");
   if (!recsel_select (se, test_2_getval, NULL))
     fail (0, 0);
+  FREEEXPR();
+  ADDEXPR ("uid =~ oo@");
+  if (!recsel_select (se, test_2_getval, NULL))
+    fail (0, 0);
+  FREEEXPR();
+  /* Again but with left anchored substring.  */
+  ADDEXPR ("-^ uid =~ foo@");
+  if (!recsel_select (se, test_2_getval, NULL))
+    fail (0, 0);
+  FREEEXPR();
+  ADDEXPR ("-^ uid =~ oo@");
+  if (recsel_select (se, test_2_getval, NULL))
+    fail (0, 0);
 
   FREEEXPR();
   ADDEXPR ("keyid == 0x12345678");

doc/gpg.texi

@@ -2561,8 +2561,8 @@ gpg can track the origin of a key. Certain origins are implicitly
 known (e.g., keyserver, web key directory) and set.  For a standard
 import the origin of the keys imported can be set with this option.
 To list the possible values use "help" for @var{string}.  Some origins
-can store an optional @var{url} argument.  That URL can appended to
-@var{string} after a comma.
+can store an optional @var{url} argument; such an URL can be appended to
+@var{string} delimited by a comma.
 
 @item --import-options @var{parameters}
 @opindex import-options
@@ -4389,6 +4389,8 @@ are:
 @table @asis
   @item --
   @var{VALUE} spans to the end of the expression.
+  @item -^
+  The substring match is left anchored.
   @item -c
   The string match in this part is done case-sensitive.
   @item -t