fix #13579 joinPath("/foo/", "../a") is now /a (#13586)

lib/pure/pathnorm.nim

@@ -76,6 +76,11 @@ proc addNormalizePath*(x: string; result: var string; state: var int;
       if (state shr 1) >= 1:
         var d = result.len
         # f/..
+        # We could handle stripping trailing sep here: foo// => foo like this:
+        # while (d-1) > (state and 1) and result[d-1] in {DirSep, AltSep}: dec d
+        # but right now we instead handle it inside os.joinPath
+
+        # strip path component: foo/bar => foo
         while (d-1) > (state and 1) and result[d-1] notin {DirSep, AltSep}:
           dec d
         if d > 0: