Normalises a stream URI so one file has exactly one key.
public://a//b.png and public://a/b.png are the same file to Drupal, and storing them under
two keys would let a delete miss and a stat disagree with a read. Rejects .. outright rather
than resolving it: a traversal here would let one site's URI address another scheme's bytes, and
there is no legitimate Drupal URI that needs one.
Normalises a stream URI so one file has exactly one key.
public://a//b.pngandpublic://a/b.pngare the same file to Drupal, and storing them under two keys would let a delete miss and a stat disagree with a read. Rejects..outright rather than resolving it: a traversal here would let one site's URI address another scheme's bytes, and there is no legitimate Drupal URI that needs one.