Missing location info if passed source files in a parent directory

[Blacksmoke16]

Bug Report

Discovered via mkdocstrings/crystal#10.

I have a class:

class Foo
  def run
    1
  end
end

That's in a directory structure like:

testing/
├── foo.cr
└── sub-dir

Generating docs for this type from the parent of testing/, the reported location of Foo#run is:

$ crystal docs --format=json --project-name= --project-version= --source-refname=master ./testing/foo.cr | oq '.program.types[0].instance_methods[0].location'
{
  "filename": "testing/foo.cr",
  "line_number": 2,
  "url": null
}

From within testing/:

$ crystal docs --format=json --project-name= --project-version= --source-refname=master ./foo.cr | oq '.program.types[0].instance_methods[0].location'
{
  "filename": "foo.cr",
  "line_number": 2,
  "url": null
}

But running it from testing/sub-dir:

$ crystal docs --format=json --project-name= --project-version= --source-refname=master ../foo.cr | oq '.program.types[0].instance_methods[0].location'
null

Fails to determine the location. Versus having the filename be ../foo.cr?

I'm not sure if this is expected or not, but at least wanted to bring it up to see what other's thoughts are.