Additionally, it would be very helpful if someone could point out the best way to use this locally for my Jekyll installation as highlighter so that I can test it more.

you can tell bundler to use a specific version of Rouge in your Gemfile:

gem "rouge", git: "https://github.com/halirutan/rouge", branch: "feat_Mathematica"

@dblessing Would you mind reviewing this PR? There is one issue and it's the reason why Travis fails: Mathematica shares the same file extension with Matlab and Objective-C

Rouge::Guesser::Ambiguous: Ambiguous guess: can't decide between ["matlab", "objective_c", "mathematica"]

@halirutan you need something like this:

lib\rouge\guessers\disambiguation.rb

      disambiguate '*.m' do
        next ObjectiveC if matches?(/@(end|implementation|protocol|property)\b/)
        next ObjectiveC if contains?('@"')

        next Mathematica if contains?('(*')

        next Matlab if matches?(/^\s*?%/)
      end

And then in the spec:

it 'guesses by filename' do
        assert_guess :filename => 'foo.wl'
        assert_guess :filename => 'foo.m', :source => '(* :Title: Collatz Visualization *)'
      end

@miparnisari Thank you very much. For the ambiguities, I used "(*" and ":=". I quickly checked the syntax of Matlab and Objective C and I think they do not have the := operator while in Mathematica, this is a very common one (far more common than including a comment).

@miparnisari Is there a particular reason, why this PR is not considered to be merged? Honestly, it is a bit frustrating that this PR is open for 7 months. I chose to implement this specifically for rogue, because it appeared to be a highly active community and as far as I could tell, rogue is very well suited for Jekyll.

If the reason for the silence is that no one here knows the Wolfram Language and cannot judge the quality, then maybe this brings some weight in: I'm also the developer for the Mathematica highlighter that is used for over 6 years on StackExchange and the Wolfram's internal forum. In addition, I'm the maintainer of the Mathematica Plugin for IntelliJ that also exists for about 6 years.

If there are any issues with the implementation here, you can assign the issue to me and I will take care of it. I'm not sure what else to say to finally get the attention of someone with push rights to the repository.

@dblessing First of all, thank you very much. Secondly, I definitely did not want to blame @miparnisari. I dearly appreciated that she helped me in the first place and I only tried to ping someone who might have a clue what's going on.

I really wonder why there are no more volunteers that would like to act as a maintainer as well for such a widely used and highly popular project. It seems your work-load is through the roof. Please take your time. I'm happy as long as I know it is on someone's list and not forgotten.