pattern: Do not use record matching.

Mes does not support it, and also the code is cleaner without it!

* gash/pattern.scm (pattern-match?, pattern-drop)
(pattern-drop-right): Avoid record matching.

gash/pattern.scm

@@ -249,7 +249,7 @@ source string is the only string that will match it."
                 (let ((start* (+ m (vector-length part))))
                   (parts-match? rest start*)))))))
 
-  (match-let ((($ <pattern> parts) pattern))
+  (let ((parts (pattern-parts pattern)))
     (if (and explicit-initial-period?
              (< start end)
              (char=? (string-ref str start) #\.))
@@ -276,13 +276,12 @@ source string is the only string that will match it."
          (#f str)
          (m (match-parts rest (+ m (vector-length part))))))))
 
-  (match-let ((($ <pattern> parts) pattern))
-    (match parts
-      (() str)
-      ((part . rest)
-       (if (string-starts-with-part str part)
-           (match-parts rest (vector-length part))
-           str)))))
+  (match (pattern-parts pattern)
+    (() str)
+    ((part . rest)
+     (if (string-starts-with-part str part)
+         (match-parts rest (vector-length part))
+         str))))
 
 (define* (pattern-drop-right pattern str #:key greedy?)
   (define (match-parts parts i)
@@ -295,12 +294,11 @@ source string is the only string that will match it."
          (#f str)
          (m (match-parts rest m))))))
 
-  (match-let ((($ <pattern> parts) pattern))
-    (let ((strap (reverse parts)))
-      (match strap
-        (() str)
-        ((part . rest)
-         (if (string-ends-with-part str part)
-             (let ((i (- (string-length str) (vector-length part))))
-               (match-parts rest i))
-             str))))))
+  (let ((strap (reverse (pattern-parts pattern))))
+    (match strap
+      (() str)
+      ((part . rest)
+       (if (string-ends-with-part str part)
+           (let ((i (- (string-length str) (vector-length part))))
+             (match-parts rest i))
+           str)))))