This seems like an obvious optimization but becomes critical when
filesystem operations even as simple as stat can result in significant
overheads; an example of this was a bespoke filesystem layer in Windows
that hosted files remotely and would download them on-demand when
particular filesystem operations occurred. Users of this system who
ensured correct file-type fileters were being used could still get
unnecessary file access resulting in large downloads.
Fixes#1657, Closes#1660
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