These are more efficient than creating buffers in place when needed.
After replacement discovered that bufNewStr() and BufNewZ() were not being used in the core code so removed them. This required using the macros in tests which is not the usual pattern.
The prior behavior on a global error (i.e. not file specific) was to write an individual error file for each WAL file being processed. On retry each of these error files would be removed, and if the error was persistent, they would then be recreated. In a busy environment this could mean tens or hundreds of thousands of files.
Another issue was that the error files could not be written until a list of WAL files to process had been generated. This was easy enough for archive-get but archive-push requires more processing and any errors that happened when generating the list would only be reported in the pgBackRest log rather than the PostgreSQL log.
Instead write a global.error file that applies to any WAL file that does not have an explicit ok or error file. This reduces churn and allows more errors to be reported directly to PostgreSQL.
The C code was assuming that the current PostgreSQL version in archive.info/backup.info was the most recent item in the history, but this is not always the case with some stanza-upgrade scenarios. If a cluster is restored from before the upgrade and stanza-upgrade is run again, it will revert db-id to the original history item.
Instead, load db-id from the db section explicitly as the Perl code does.
This did not affect archive-get since it does a reverse scan through the history versions and does not rely on the current version.
This new implementation should behave exactly like the old Perl code with the exception of a few updated log messages.
Remove as much of the Perl code as possible without breaking other commands.
There was a lot of extra boilerplate involved in setting up pipes so that is now automated.
In some cases testing with multiple children is useful so allow that as well.
