Add MlintBear

[li-boxuan]

Perform lint check on Matlab code.

Closes #2352

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[li-boxuan]

I have some concerns here:

1. Users need to add mlint executable to PATH. For example, on a Mac with MATLAB_R2017a installed:

   export PATH="/Applications/MATLAB_R2017a.app/bin/maci64:$PATH"

   I wonder where I should put this instruction?

2. I used lengthofline.m and lengthofline2.m as test files. They are copied from Matlab sample code (See MathWorks copyright on both files) . Would it be a copyright issue?

[ankitxjoshi]

@li-boxuan adding the executable to the environment path is a basic requirement for many linters, if one wishes to execute them using CLI. This could happen with most of the linters. The error message submitted by coala would simply be executable not installed. Modifying it just for this special case IMO is not necessary.
As for the copyright issue is it necessary to use MathWord code? Can't you come up with some test cases of your own?

[li-boxuan]

@MacBox7 Thanks for comments!

adding the executable to the environment path is a basic requirement for many linters

This case is special to me because it is not trivial to find the mlint executable. It is not documented on Matlab website (They don't even tell users that there is such an executable; they only say mlint is a function call in Matlab). I didn't know the existence of mlint executable until I saw https://github.com/Gimly/vscode-matlab/blob/master/README.md.

Can't you come up with some test cases of your own?

Yes, sure. The reason I used official examples is that I found them pretty nice and this would be consistent with the example on https://www.mathworks.com/help/matlab/ref/mlint.html. I would write my own test cases if it's necessary (but may not be as good as official ones).

[jayvdb]

definitely cant accept with example code from non-free sources.

Also, a decision re non-free linters, they should be in their own repo, at https://gitlab.com/coala/non-free-linter-bears , so they dont cause a maintenance burden on the rest of coala, and so they can have specific documentation about each, and also we can start to build a different infrastructure in that repository for them.

[jayvdb]

I've closed the issue.
We can leave this PR open for a while, until you've migrated the bear to the new repo.

[jayvdb]

Looks like this wont be migrated until after GSoC. Closing