Symlinked files are ignored

depcheck does not process source files that are symlinked to a file outside the package being analyzed.

This is simple to repro:

1. Create a new package with a blank package.json
2. Add a js file where the only line is var test = require('lodash');
3. Running depcheck on that package properly shows that the dependency lodash is missing
4. Move the js file somewhere outside the package and symlink to it inside the package
5. depcheck reports no issues

I found the problematic code: only regular files (the type ‘file’) are checked. This group does not include the ‘link’ category, which contains the symlinks in question. That’s why they’re ignored.

Context: the reason I have to worry about symlinks is that I’m using this within a bazel build system, which symlinks groups of source files to sandbox environments where tests run.

[magillj]

Sure I might be able to give it a shot within the next couple weeks

[mzyil]

I’m planning to open a PR anyway, I will see what I can do