Added checks for `--delta` and `--force` restore options to ensure that the destination is a valid $PGDATA directory. pgBackRest will check for the presence of `PG_VERSION` or `backup.manifest` (left over from an aborted restore). If neither is found then `--delta` and `--force` will be disabled but the restore will proceed unless there are files in the $PGDATA directory (or any tablespace directories) in which case the operation will be aborted.
Keepalives are now used to make sure the remote for the main process does not timeout while the thread remotes do all the work. The error messages for timeouts was also improved to make debugging easier.
1) Started on a general markdown renderer
2) Internal links now work in PDF
3) Improvements to PDF styling
4) Some comment and formatting fixes
5) User guide edits.
* Better messaging for expiration.
* Fixed already stopped message.
* retention-archive and retention-archive-type now use retention-full and 'full' when not specified.
* Fixed issue where backup-user was required (should default to backrest).
* ExecuteTest now supports retries.
* Fixed issue where log test was not comparing test logs.
* Fixed issue where test logs would not match for ssh connection errors
