>>1536538A lot of cyclocross bikes, especially in the past, had all the cable routing on the top tube, but they used road components. So the front derailleur cable would come from the top, but need to pull from the bottom. Many of the frames had a built-in pulley to accommodate this like pic related. There are still clamp-on versions that you can buy to accomplish the same thing.
https://problemsolversbike.com/products/shifters-derailleurs/cross_clamp_-_17312 