I was trying github.com/transparency-dev/incubator/vindex/cmd/sumdbverify@main --mod_root /host in a container, where /host was a read-only mount of a git checkout on the container host. In this setup, I had an ownership mismatch, and I got somewhat confusing error messaged from sumdbverify: failed to create zip file: create zip from version control system /host: could not find a recognized version control system at "/host".
When I ran git directly, e.g., (cd /host && git log) I got a better error message that explained the problem
fatal: detected dubious ownership in repository at '/host'
To add an exception for this directory, call:
git config --global --add safe.directory /host
It would be nice if the sumdbverify error reporting mentioned unexpected ownership, rather than telling me that there's no git repository.
(And running the suggested git config command solved the problem, and made sumdbverify happy).