The subtree was moved from "shared/c-siphash" to "src/c-siphash". That confuses
git-subtree. To fix it, reimport the code with
rm -rf src/c-siphash
git commit -a -m 'dummy commit'
git subtree add --prefix src/c-siphash git@github.com:c-util/c-siphash.git eb87a9c4a5b0441ede073597253e1d0b7785e6be --squash
Then rebase the result to drop the bogus dummy commit from the history.
To update the library use:
git subtree pull --prefix src/c-siphash git@github.com:c-util/c-siphash.git main --squash
