[Done](https://github.com/libgit2/libgit2/blob/8b00c3124228b3e224be6095216c0ff925b437b1/src/object.c#L368-L402) and [done](https://github.com/libgit2/libgit2/blob/8b00c3124228b3e224be6095216c0ff925b437b1/tests-clar/object/lookupbypath.c)!