f27b3371eb
Add documentation explaining how ext4's directory hash algorithm selection works based on the platform's char signedness. GCC automatically defines __CHAR_UNSIGNED__ on platforms where char is unsigned (e.g., ARM), which affects the hash algorithm used. The filesystem stores the hash variant in the superblock flags, ensuring correct operation regardless of the mounting platform. Co-developed-by: Claude <noreply@anthropic.com> Signed-off-by: Simon Glass <simon.glass@canonical.com>