1) Re-checksums files that have checksums in the manifest
2) Recopies files that do not have a checksum
3) Saves the manifest at regular intervals to preserve checksums
4) Unit tests for all cases (that I can think of)
* Fixed a buffering error that could occur on large, highly-compressible files when copying to an uncompressed remote destination. The error was detected in the decompression code and resulted in a failed backup rather than corruption so it should not affect successful backups made with previous versions.
* Pushing duplicate WAL now generates an error. This worked before only if checksums were disabled.
* Database System IDs are used to make sure that all WAL in an archive matches up. This should help prevent misconfigurations that send WAL from multiple clusters to the same archive.
* Regression tests working back to PostgreSQL 8.3.
* Improved threading model by starting threads early and terminating them late.
* Added restore functionality.
* All options can now be set on the command-line making pg_backrest.conf optional.
* De/compression is now performed without threads and checksum/size is calculated in stream. That means file checksums are no longer optional.
* Added option `--no-start-stop` to allow backups when Postgres is shut down. If `postmaster.pid` is present then `--force` is required to make the backup run (though if Postgres is running an inconsistent backup will likely be created). This option was added primarily for the purpose of unit testing, but there may be applications in the real world as well.
* Fixed broken checksums and now they work with normal and resumed backups. Finally realized that checksums and checksum deltas should be functionally separated and this simplied a number of things. Issue #28 has been created for checksum deltas.
* Fixed an issue where a backup could be resumed from an aborted backup that didn't have the same type and prior backup.
* Removed dependency on Moose. It wasn't being used extensively and makes for longer startup times.
* Checksum for backup.manifest to detect corrupted/modified manifest.
* Link `latest` always points to the last backup. This has been added for convenience and to make restores simpler.
* More comprehensive unit tests in all areas.
