Option '--keys-dir' is used for redefinition of default directories with
public/revoked keys. If keys directory is set then default directories
are ignored and target directory is expected to contain following
structure for ed25519 signature mechanism:
dir/
trusted.ed25519 <- file with trusted keys
revoked.ed25519 <- file with revoked keys
trusted.ed25519.d/ <- directory with files containing trusted keys
revoked.ed25519.d/ <- directory with files containing revoked keys
Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>