Previous component-wise path comparison is recursive and generates a
large amount of garbage. This more efficient version simply replaces the
path comparison with the zero-value to sort before everything. We do
this by replacing the byte-wise comparison that swaps a single character
inline for the separator comparison, such that separators sort first.
The resulting implementation provides component-wise path comparison
with no cost incurred for allocation or stack frame.
Direction of the comparison is also reversed to match Go style.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
bba5a0d05c