Ruleset::processRule(): fix handling of rules included via path

This fixes a bug where properties set for rules included via a path to the sniff file or to an included standards file, would be disregarded if the slashes used in the path did not match the slashes expected for the OS on which the ruleset is being run.

Fixes 2497

src/Ruleset.php

@@ -861,11 +861,17 @@ private function processRule($rule, $newSniffs, $depth=0)
         $ref  = (string) $rule['ref'];
         $todo = [$ref];
 
-        $parts = explode('.', $ref);
-        if (count($parts) <= 2) {
-            // We are processing a standard or a category of sniffs.
+        $parts      = explode('.', $ref);
+        $partsCount = count($parts);
+        if ($partsCount <= 2 || $partsCount > count(array_filter($parts))) {
+            // We are processing a standard, a category of sniffs or a relative path inclusion.
             foreach ($newSniffs as $sniffFile) {
-                $parts         = explode(DIRECTORY_SEPARATOR, $sniffFile);
+                $parts = explode(DIRECTORY_SEPARATOR, $sniffFile);
+                if (count($parts) === 1 && DIRECTORY_SEPARATOR === '\\') {
+                    // Path using forward slashes while running on Windows.
+                    $parts = explode('/', $sniffFile);
+                }
+
                 $sniffName     = array_pop($parts);
                 $sniffCategory = array_pop($parts);
                 array_pop($parts);