We skip all issues from autogenerated files.
Also reuse AST parsing for nolint and autogenerated exclude processors:
decrease processing time on golang source code from 3s to 800ms.
As observed in #30, there's tools out there that don't comply 100% with
the referenced golang convention.
With this change, golangci-lint will skip some more of those generated
files.
Signed-off-by: Stephan Renatus <srenatus@chef.io>
