pxar: match_pattern: impl invert() to switch the match type of a MatchPattern.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

src/pxar/match_pattern.rs

@@ -202,6 +202,11 @@ impl MatchPattern {
 
         MatchPatternSlice::to_bytes(&slices)
     }
+
+    /// Invert the match type for this MatchPattern.
+    pub fn invert(&mut self) {
+        self.match_positive = !self.match_positive;
+    }
 }
 
 #[derive(Clone)]