I suspect postgress just brings efficient queries. My initial thought was how fossil uses sqlite as a backing store. but... not only is sqlite intentionally designed as an interchange format(stable specification). the postgress disk structure is intentionally designed to not be a interchange format(they reserve the right to change it at any time) so not that.

So the only real reason is you already have a postgres server and want the efficient query indexes.

As an interesting side note. I found this document on the internal data structure of fossil. https://fossil-scm.org/home/doc/trunk/www/fossil-is-not-rela...

as the other replies mention, efficient querying can be fun https://oseifert.ch/blog/building-pgit

This seems like the elephant in the room.

I'm not saying this project isn't cool, but whenever you have ANY software that's designed to be hosted A-style, and you host it B-style, the obvious question is "Why not host it the A way?"