The primary source for project info is now src/version.h.
The pgBackRestDoc::ProjectInfo module loads the project info from src/version.h at runtime so there is no need to update it.
This is consistent with the way BackRest and BackRest test were renamed way back in 18fd2523.
More modules will be moving to pgBackRestDoc soon so renaming now reduces churn later.
This directory was once the home of the production Perl code but since f0ef73db this is no longer true.
Move the modules to test in most cases, except where the module is expected to be useful for the doc engine beyond the expected lifetime of the Perl test code (about a year if all goes well).
The exception is pgBackRest::Version which requires more work to migrate since it is used to track pgBackRest versions.
These constants are easier than using cfgOptionName() and cfgCommandName() and lead to cleaner code and simpler to construct messages.
String versions are provided. Eventually all the strings will be used in the config structures, but for now they are useful to avoid wrapping with strNew().
