Sorting semantic versions using pattern policy

[paul-carlton]

I want to use image automation with semantic versions but our devs cut images with components to fix a base verison, i.e. 0.4.15 is less than 0.4.15-rc1 to them. This is because when releasing to prod they take a semantic version like 0.4.15 and do release testing, creating 0.4.15-rcN images until they are happy. This is, of course, not how the semantic version spec works! They can't create 0.4.16 because that already exists. I initially addressed this by removing the base image from our image repo when a 'pre-release' version was created. However this denies us the opportunity of falling back to the base image if we want and is complicated to implement, so is not a good solution. I decided to use the pattern policy instead of semver policy but alphabetic sort of semantic versions prefers 0.4.8 over 0.4.15 and numerical sort finds a semantic version invalid!