Am I missing something? I see a lot about how to install and run this "tool for pattern matching and text transformation", but basically nothing that concretely explains how to tell it what patterns to match or text transformations to apply. It seems to be using a language called "SmPL" for this but I had to do a separate search for that and even then the only real documentation I could find was a reference grammar (https://coccinelle.gitlabpages.inria.fr/website/docs/main_gr...).
I assume the OP recently watched the video of Ryan C. Gordon porting ioquake3 from SDL2 to SDL3 [1]. He uses the linked tool to automate a lot of the migration. SDL3 ships with a Coccinelle file [2] to handle all the Enum and API renames and it also comments areas that need manual fixing.
[1] https://ioquake3.org/ioquake3/ryan-c-gordon-ports-ioquake3-f...
[2] https://github.com/libsdl-org/SDL/blob/main/build-scripts/SD...
Looks like the documentation is bundled along with the software (I had to install coccinelle-doc on Debian). It seems fairly comprehensible to me.
Coccinelle is French for lady bug. Cool tool. It's been around for what feels like forever but outside of the Kernel, people unfortunately still seem to prefer regex.
I also met Julia when I did an exchange semester at diku, Copenhagen, DK. She's really nice. :)