.capnp files in a subtree #217

1. 
   rustaceanrob commented at 2:16 pm on September 24, 2025: none

   After revisiting #174, a client can take the capnp files from bitcoin/src/ipc/capnp with essentially no changes and use them to generate client code in their target language. Would it make sense to add these to a separate repository and tag them per each release in Bitcoin Core? i.e. if I would like to build on v0.30 IPC interface, I would clone the capnp file repository and checkout the v0.30 tag.

   Perhaps related to #54, maybe these tags are not dependent on Bitcoin Core and reflect the semantic versioning of the capnp schema.

2. 
   Sjors commented at 2:25 pm on September 24, 2025: member

   It’s likely that the interface will be stable throughout each major Bitcoin Core version, e.g. v30.x.

   Apparently it’s not possible to clone just a subdirectory and the Bitcoin Core repo is huge, so maybe a subtree does make sense.

   However it would add quite a bit of overhead on the Bitcoin Core side to make changes.

3. 
   TheCharlatan commented at 2:56 pm on September 24, 2025: collaborator

   I still think they should just be installed by Bitcoin Core in something like include/capnp.
4. 
   ryanofsky commented at 3:45 pm on September 24, 2025: collaborator

   Yes I think a good solution to this is to install the files and maybe include them in binary releases.

   Cap’n Proto and and libmultiprocess (when build standalone) do already install files like /capnp/c++.capnp and /mp/proxy.capnp, and there’s no reason bitcoin can’t do the same with it’s own files.

   The git cloning situation is awkward, but moving the files to a different repository could create a lot of problems, because the src/ipc/capnp/ files need to be kept in sync with the src/interface/ files otherwise the build breaks, so it is nice to be able to update both atomically.

5. 
   ryanofsky commented at 3:46 pm on September 24, 2025: collaborator

   Maybe github can support features like https://josh-project.github.io/josh/intro.html to make partial cloning easier someday too

Contributors
rustaceanrob Sjors TheCharlatan ryanofsky