Historically, newsyslog compressed rotated log files to save disk space. This was
useful in the early days, but with the advent of modern file systems like ZFS,
which offer native compression, and the availability of larger hard drives, the
benefits of additional compression are less compelling. This is especially true
considering the inconvenience of having to decompress log files when searching
for specific patterns.
Additionally, the historical implementation of compression methods lacks
future-proofing. Therefore, we have redefined the J, X, Y, Z flags to mean
"treat the file as compressible" instead of "compress the file with that particular
method". A new command line option, -c, has been introduced to override these
settings in a future-proof manner. The following choices are now available:
none - default: do not compress, regardless of flag.
legacy - historical behavior: J=bzip2, X=xz, Y=zstd, Z=gzip.
bzip2, xz, zstd, gzip - use the specified compression method.