Features:

• Add lz4 compression support. Note that setting compress-type=lz4 will make new backups and archive incompatible (unrestorable) with prior versions of pgBackRest. (Reviewed by Cynthia Shang.)
• Add --dry-run option to the expire command. Use dry-run to see which backups/archive would be removed by the expire command without actually removing anything. (Contributed by Cynthia Shang, Luca Ferrari.)

Improvements:

• Improve performance of remote manifest build. (Suggested by Jens Wilke.)
• Fix detection of keepalive options on Linux. (Contributed by Marc Cousin.)
• Add configure host detection to set standards flags correctly. (Contributed by Marc Cousin.)
• Remove compress/compress-level options from commands where unused. These commands (e.g. restore, archive-get) never used the compress options but allowed them to be passed on the command line. Now they will error when these options are passed on the command line. If these errors occur then remove the unused options. (Reviewed by Cynthia Shang.)
• Limit backup file copy size to size reported at backup start. If a file grows during the backup it will be reconstructed by WAL replay during recovery so there is no need to copy the additional data. (Reviewed by Cynthia Shang.)