Fix typo in regex.

The original author almost certainly intended to match the literal dash character '-' but ended up matching a range of other characters instead.

PiperOrigin-RevId: 445555501
Change-Id: Iaea456de99b2747703fdaa2a8cf136eba1b75ce8

Move private packages to the internal/ subdirectory.

Fixes #3.

PiperOrigin-RevId: 319754294
Change-Id: I9988398913e3595d137185496b379b589a0b380b

Internal change

PiperOrigin-RevId: 318727811
Change-Id: I08d001c99a62132f240e241da6179a99915862e6