meta4ra -- Metalink4 utilities

meta4-create utility is used to create Metalink4
(https://datatracker.ietf.org/doc/html/rfc5854)
.meta4-file for single specified file.

-fn NAME      -- the only required option specifying file's name.
-desc "..."   -- set file's description.
-mtime FILE   -- let published date be equal to FILE's mtime.
-sig-pgp .asc -- path to armored OpenPGP's signature file.
-sig-ssh .sig -- path to armored OpenSSH's signature file.
-torrent URL  -- set BitTorrent's URL.
-hashes -- comma-separated list of colon-separated pairs of hash'es
           name and the external command used to compute it. Command
           shall take the data from stdin and print the digest in
           hexadecimal form with the following newline to stdout.

Following hashes are predefined by default:

* sha-256:sha256 -- standardized name; standard command in many OSes
                    May be fast on hardware accelerated CPUs.
* sha-512:sha512 -- standardized name; standard command in many OSes
                    Faster on 64-bit CPUs than software sha-256.
* skein-256:skein256 -- non-standardized name; out-of-box command in FreeBSD
                        Faster than software sha-*/shake*.
* skein-512:skein512 -- non-standardized name; out-of-box command in FreeBSD
                        Faster on 64-bit CPUs than skein-256.
* shake128:goshake128 -- standardized name; non-standard command
                         Faster than software sha-*. Much faster on hardware.
* shake256:goshake256 -- standardized name; non-standard command
                         Same speed as sha-512 on 64-bit CPUs.
                         Much faster on hardware.
* streebog-256:streebog256sum -- non-standardized name; command is in contrib/
* streebog-512:streebog512sum -- non-standardized name; command is in contrib/
* blake3-256:b3sum -- non-standardized name; additional package in most OSes
                      Fastest parallelizeable software hash

SHA2 and SHA3 (SHAKE*) are USA's NIST standards. Streebog is Russian
Federation's government standard. Skein is SHA3-finalist. BLAKE3 is
reduced round Merklee-tree-based BLAKE2 descendant. BLAKE2 is reduced
round BLAKE, that also was one of SHA3-finalists.

meta4-check utility is used to check files against provided Metalink4.

-extract-sig -- store the OpenPGP signature (if exists) in .asc file nearby.
-hashes      -- same as in meta4-create. Hashes are sorted by preferences
                priority. First matching one will be used to check integrity.