path: remove unnecessary string copies

As the length of `path` is known at this point, there is no point in
making an exact copy using `slice`.

Backport-PR-URL: #14787
PR-URL: #14438
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Timothy Gu <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Khaidi Chu <[email protected]>

Author: tniessen

lib/path.js

@@ -767,7 +767,9 @@ const win32 = {
         }
       }
     } else if (code === 47/*/*/ || code === 92/*\*/) {
-      return path[0];
+      // `path` contains just a path separator, exit early to avoid
+      // unnecessary work
+      return path;
     }
 
     for (var i = len - 1; i >= offset; --i) {
@@ -1031,23 +1033,23 @@ const win32 = {
               if (len === 3) {
                 // `path` contains just a drive root, exit early to avoid
                 // unnecessary work
-                ret.root = ret.dir = path.slice(0, 3);
+                ret.root = ret.dir = path;
                 return ret;
               }
               rootEnd = 3;
             }
           } else {
             // `path` contains just a drive root, exit early to avoid
             // unnecessary work
-            ret.root = ret.dir = path.slice(0, 2);
+            ret.root = ret.dir = path;
             return ret;
           }
         }
       }
     } else if (code === 47/*/*/ || code === 92/*\*/) {
       // `path` contains just a path separator, exit early to avoid
       // unnecessary work
-      ret.root = ret.dir = path[0];
+      ret.root = ret.dir = path;
       return ret;
     }