Debugging use of ignore

Hello! This is tangentially related to #196, as I'm attempting to use `.buckconfig`'s project.ignore setting to avoid loading paths that have troublesome symlinks in them altogether.

So a tree like:

* bin/veritech/node_modules -> bin/lang-sj
* bin/lang-js

Causes the issue in #196 - the file watcher picks up the `package.json` file in the symlinked directory first, causing the source to not be updated when package.json changes (and thereby not retrigger a build).

In an attempt to avoid this, I thought I would use the following in the `.buckconfig` in the root:

```
[project]
ignore = **/node_modules/**
```

But it appears to not work?

If I add something like:

```
[project]
ignore = .git
```

It does appear to successfully ignore files in the .git tree. Is there a good way to debug what files are being tracked, and how they are evaluated against the ignore list?