Given an entry file and a target file, track down any files that are requiring the target file.
Usage: backtrack-require <entry> <target>Find every file that is requiring `target`, given an`entry` file.
$ backtrack-require fixtures/a.js fixtures/c.jsfixtures/b.jsfixtures/d.js
entry and a
target file, call the
done callback with an array
of files that are requiring
MIT. See LICENSE.md for details.