The API of the package is as follows:
    func Equal(x, y interface{}, opts ...Option) bool
    func Diff(x, y interface{}, opts ...Option) string

    type Option interface{ ... }
        func Ignore() Option
        func Comparer(f interface{}) Option
        func Transformer(name string, f interface{}) Option

        func FilterPath(f func(Path) bool, opt Option) Option
        func FilterValues(f interface{}, opt Option) Option

        func AllowUnexported(typs ...interface{}) Option
    type Options []Option

    type Path []PathStep
    type PathStep interface{ ... }

    type Indirect interface{ ... }
    type StructField interface{ ... }
    type MapIndex interface{ ... }
    type SliceIndex interface{ ... }
    type TypeAssertion interface{ ... }
    type Transform interface{ ... }

See the package docs in compare.go for a high-level view of this package.