public static String comparableQualifier(String qualifier) {
            int i = _QUALIFIERS.indexOf(qualifier);

            return i == -1 ? (_QUALIFIERS.size() + "-" + qualifier) : String.valueOf(i);
        }
Returns a comparable value for a qualifier.

This method takes into account the ordering of known qualifiers then unknown qualifiers with lexical
ordering.

just returning an Integer with the index here is faster, but requires a lot of if/then/else to check for -1
or QUALIFIERS.size and then resort to lexical ordering. Most comparisons are decided by the first character,
so this is still fast. If more characters are needed then it requires a lexical sort anyway.

@param qualifier
@return an equivalent value that can be used with lexical comparison
plugin/src/main/java/com/mcxiaoke/packer/ng/StringVersion.java