Code review comment for ~mdeslaur/ubuntu-cve-tracker:perf-part2

Thanks for working on this Marc - I'll give it a run locally.

@seth-arnold - regarding realpath - I added thus to support reading a CVE from stdin for check-syntax - ie:

./scripts/check-syntax --stdin < active/CVE-YYYY-NNNNN

(since this then allows to support integrating check-syntax with an external editor for on-the-fly syntax checking).

But performance improvements are more important than having this work at the moment so I am more than happy to forego it whilst we get performance improved, then I can look to add it back if it is still needed (and try and retain the performance gains in the process).