Add support for gitmail options 'true' and 'false'

When processing config options, we now treat these strings as
'1' and '0' so that they can be used as booleans. (Previously,
'false' would evaluate to true by perl string rules.)

tools/git/gitmail

@@ -319,6 +319,7 @@ my $STDERRNULL = " 2> /dev/null";
 ######################################################################
 # Function Prototypes
 ######################################################################
+sub fix_truefalse($);
 sub change_type($$$);
 sub ref_type($);
 sub rev_type($);
@@ -1191,9 +1192,31 @@ sub debug(@) {
     }
 }
 
+#
+# Return the input value, unless it's 'true' (in which case return 1), or
+# 'false' (in which case return 0)
+#
+# Intended to be used by map'ing over arrays of config options
+#
+sub fix_truefalse($) {
+    my ($val) = @_;
+    if (defined($val)) {
+        if ($val eq 'true') {
+            return 1;
+        } elsif ($val eq 'false') {
+            return 0;
+        } else {
+            return $val;
+        }
+    } else {
+        return $val;
+    }
+}
+
 #
 # Return either the config value associated with the repo or the second
 # argument, which supplies the default.
+# Note: 'true' and 'false' are special values, which turn into '1' and '0'
 #
 sub get_config($$) {
     my ($var,$default) = @_;
@@ -1218,12 +1241,12 @@ sub get_config($$) {
                 if ($multivalue) {
                     push @values, $value;
                 } else {
-                    return $value;
+                    return fix_truefalse($value);
                 }
             }
         }
         if ($multivalue && (@values > 0)) {
-            return @values;
+            return map {fix_truefalse($_)} @values;
         }
     }
 
@@ -1242,15 +1265,15 @@ sub get_config($$) {
             foreach my $value (@value) {
                 debug("Got $value from git config for $var");
             }
-            return @value;
+            return map {fix_truefalse($_)} @value;
         } else {
             debug("Got $value[0] from git config for $var");
-            return $value[0];
+            return fix_truefalse($value[0]);
         }
     } else {
         if (!$multivalue) {
             debug("Using " , defined($default)?$default : "(undef)" , " for $var");
-            return $default;
+            return fix_truefalse($default);
         } else {
             # Multivalue always returns the empty array for the defauly
             debug("Using the emtpy list for $var");