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Using FindFirstFileExW() requires the OS to allocate a 64K buffer for each directory and then free it when we call FindClose(). Update fscache to call the underlying kernel API NtQueryDirectoryFile so that we can do the buffer management ourselves. That allows us to allocate a single buffer for the lifetime of the cache and reuse it for each directory. This change improves performance of 'git status' by 18% in a repo with ~200K files and 30k folders. Documentation for NtQueryDirectoryFile can be found at: https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/content/ntifs/nf-ntifs-ntquerydirectoryfile https://docs.microsoft.com/en-us/windows/desktop/FileIO/file-attribute-constants https://docs.microsoft.com/en-us/windows/desktop/fileio/reparse-point-tags To determine if the specified directory is a symbolic link, inspect the FileAttributes member to see if the FILE_ATTRIBUTE_REPARSE_POINT flag is set. If so, EaSize will contain the reparse tag (this is a so far undocumented feature, but confirmed by the NTFS developers). To determine if the reparse point is a symbolic link (and not some other form of reparse point), test whether the tag value equals the value IO_REPARSE_TAG_SYMLINK. Signed-off-by: Ben Peart <benpeart@microsoft.com>