Use Path::get() in chdir function to support .. path nav (#1104)

Author: nnh12

kernel/environment/src/lib.rs

@@ -31,17 +31,14 @@ impl Environment {
     /// Changes the current working directory.
     #[doc(alias("change"))]
     pub fn chdir(&mut self, path: &Path) -> Result<()> {
-        for component in path.components() {
-            let new = self.working_dir.lock().get(component.as_ref());
-            match new {
-                Some(FileOrDir::Dir(dir)) => {
-                    self.working_dir = dir;
-                }
-                Some(FileOrDir::File(_)) => return Err(Error::NotADirectory),
-                None => return Err(Error::NotFound),
+        match path.get(&self.working_dir) {
+            Some(FileOrDir::Dir(dir)) => {
+                self.working_dir = dir;
+                Ok(())
             }
+            Some(FileOrDir::File(_)) => Err(Error::NotADirectory),
+            None => Err(Error::NotFound),
         }
-        Ok(())
     }
 
     /// Returns the value of the environment variable with the given `key`.