The Go tool supports recursively looking up dependencies that may be vendored in ./vendor directories and their parents. It seems that dep doesn't support vendoring dependencies in nested dirs. Example:

src/do.co/monorepo/vendor
src/do.co/monorepo/large_project/with_many/specific_needs/vendor

In this example, monorepo/vendor contains global, generally needed dependencies that may have been vendored using another tool, while monorepo/large_project/with_many/specific_needs/vendor contains dependencies needed only by that project, which we want to use dep to manage.

This seems to currently not be possible. dep appears to be ignoring the dependencies vendored in monorepo/vendor and try to pull them again in monorepo/large_project/with_many/specific_needs/vendor.