I just had an issue in which I changed the repo of a package I had been using (use-package), to a fork of that package. Making that change in Straight proved that either there needs to be an easy way, or I need to know the easy way. Due to conflicting recipes I ended up changing the use-package statement (expected), editing the straight cache file (ugh), manually deleting folders in /repos and /builds, and restarting emacs.

How should one go about switching repos on an already used package without all this to-do?¹

Answer

M-x straight-normalize-package does the trick after you change the repo. Normalize serves to update location.

Footnotes

¹ Question and its full answer in stupendous rapidity here: https://github.com/raxod502/straight.el/issues/751