An upcoming mappings updater that is work in progress currently.
This updater allows it to update Spigot NMS mappings using transition mappings. Transition mappings are mappings generated by getting the obfuscated names of two targeted versions.
obf_name_1.15.2 <-> clear_name_1.15.2 <-> clear_name_20w16a <-> obf_name_20w16a
In the end we have the transition mappings.
obf_name_1.15.2 <-> obf_name_20w16a
Now we can easily load Spigot mappings for 1.15.2
spigot_mappings_1.15.2 <-> obf_name_1.15.2 <-> obf_name_20w16a <-> spigot_mappings_20w16a