Generate list of Perl versions from CPAN mirror and parsed reports

[preaction]

There is a perl_version table which caches the known list of Perl versions for easy reference. This table was maintained by the main report processing task (CPAN::Testers::Data::Generator). We need a way to build this table from scratch using data from the local CPAN mirror.

We should have one module, CPAN::Testers::Backend::ProcessPerlVersion. This module should be a runnable module (Beam::Runnable) that, when run, does the following:

• Clear the current cache completely (optional, with --clear command-line option)
• Insert cache rows by reading the local CPAN mirror directory (directory must be configurable as an attribute)

This will require a DBIx::Class module be built to read/write the perl_version table (CPAN::Testers::Schema::Result::PerlVersion, in cpan-testers/cpantesters-schema). It could be easier to build the method that reads the CPAN directory in a CPAN::Testers::Schema::ResultSet::PerlVersion class (it's better design to push as much data/business logic into the model layer).

[preaction]

I've added the script that will populate Perl versions from the local CPAN mirror, but this is insufficient. Two things remain on this ticket:

• [ ] A cron job needs to be configured to run the scan from the CPAN mirror. This should be added to the Rexfile (unless cpan-testers/cpantesters-deploy#31 is done, then the cron job should be configured in cpantesters-deploy)
• [ ] The ProcessReports module needs to ensure that the Perl version in the report is also in the database.

The second task is necessary mostly because of patched Perls or other Perls that are not released on CPAN. For every report processed by ProcessReports, it should call the ensure_exists method of the PerlVersion resultset (see cpan-testers/cpantesters-schema#23).

[preaction]

We also need to fix the existing data: There are cpanstats lines without a corresponding row in the perl_versions table. We should add a FixPerlVersions command that will look for these rows and add them. The query to just find missing entries is:

select distinct cpanstats.perl 
from cpanstats 
left join perl_version on perl_version.version = cpanstats.perl
where cpanstats.perl != "0" and perl_version.version is null;

The "0" Perl version seems to be from some reporter back in the day. None of these records are more recent than 2010.