Add option to exclude specific directories

[jeff-matthews]

Fixes #49

I added some logic to the generator.rb file to exclude directories specified in a project's _config.yml file like so:

jekyll_relative_links:
  exclude:
    - directory

The plugin still seems to be processing all directories though because I don't see confirmation in the console that the specified directories have been excluded when it gets to the jekyll-relative-links stage:

bundle exec jekyll build --trace --verbose
  Logging at level: debug
Configuration file: /Users/jeffmatthews/git/devdocs/_config.yml
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/page-canonical-url.rb
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/last-modified-at.rb
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/page-baseurl-generator.rb
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/collapsible-content.rb
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/glossary-tooltip.rb
         Requiring: /Users/jeffmatthews/git/devdocs/_plugins/remote_markdown.rb
         Requiring: jekyll-sitemap
         Requiring: jekyll-redirect-from
         Requiring: jekyll-titles-from-headings
         Requiring: jekyll-optional-front-matter
         Requiring: jekyll-relative-links
            Source: /Users/jeffmatthews/git/devdocs
       Destination: /Users/jeffmatthews/git/devdocs/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
       EntryFilter: excluded /bin
       EntryFilter: excluded /scss
       EntryFilter: excluded /rakelib
       EntryFilter: excluded /README.md
       EntryFilter: excluded /Rakefile
       EntryFilter: excluded /package-lock.json
       EntryFilter: excluded /package.json
       EntryFilter: excluded /Gemfile
       EntryFilter: excluded /Gemfile.lock
           Reading: _videos/fundamentals/create-a-new-module.md
           Reading: _videos/fundamentals/add-new-product-attribute.md
           Reading: _videos/fundamentals/index.md
           Reading: _videos/fundamentals/create-a-new-page.md
           Reading: _videos/fundamentals/add-a-new-table-to-database.md
           Reading: _videos/fundamentals/add-a-javascript-module.md
           Reading: _videos/index.html
        Generating: JekyllRedirectFrom::Generator finished in 9.121496 seconds.
        Generating: JekyllOptionalFrontMatter::Generator finished in 2.861665 seconds.
        Generating: Jekyll::JekyllSitemap finished in 0.002033 seconds.
        Generating: JekyllTitlesFromHeadings::Generator finished in 0.109857 seconds.
        Generating: JekyllRelativeLinks::Generator finished in 670.421584 seconds.
...

[benbalter]

@jeff-matthews Thanks for this. I moved things around a bit to better conform to Ruby style, and added tests. I believe things should now be working as expected. Mind giving it another try?

If things look good, if you wouldn't mind documenting the new behavior in the README, I believe this PR can be merged and I can cut a new release.

[jeff-matthews]

Thanks @benbalter! I pulled your changes, but I'm getting an error:

bundler: failed to load command: jekyll (/Users/jeffmatthews/.rvm/gems/ruby-2.5.3/bin/jekyll)
NoMethodError: undefined method `config' for #<Jekyll::Configuration:0x00007fda99e0fe18>
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/filters/url_filters.rb:55:in `sanitized_baseurl'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/filters/url_filters.rb:35:in `relative_url'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:91:in `url_for_path'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:55:in `block in replace_relative_links!'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:50:in `gsub'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:50:in `replace_relative_links!'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:42:in `block in generate'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:37:in `each'
  /Users/jeffmatthews/git/forks/jekyll-relative-links/lib/jekyll-relative-links/generator.rb:37:in `generate'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/site.rb:174:in `block in generate'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/site.rb:172:in `each'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/site.rb:172:in `generate'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/site.rb:72:in `process'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/command.rb:28:in `process_site'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/commands/build.rb:65:in `build'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/commands/build.rb:36:in `process'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/gems/jekyll-3.7.4/exe/jekyll:15:in `<top (required)>'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/bin/jekyll:23:in `load'
  /Users/jeffmatthews/.rvm/gems/ruby-2.5.3/bin/jekyll:23:in `<top (required)>'```

[benbalter]

@jeff-matthews sorry about that. You actually found a long-standing bug, and I think a long-standing mistake in the Jekyll documentation. I'll open an issue upstream, but things should be fixed here and I can build locally outside of tests. Mind giving it another try?

[jeff-matthews]

@benbalter, works like a charm! Generation time in my particular project went from ~670 seconds to ~4 seconds, which is a huge improvement. I'll update the README with the new behavior and push those changes to this PR.

[welcome]

Congrats on getting your first pull request to Jekyll Relative Links merged! Without amazing humans like you submitting pull requests, we couldn’t run this project. You rock! 🎉

If you're interested in tackling another bug or feature, take a look at the open issues, especially those labeled help wanted.

[benbalter]

Thanks @jeff-matthews!

[jeff-matthews]

Thank you @benbalter!!!