It turned out that changes like
https://github.com/kubernetes-csi/csi-lib-utils/pull/33 should better
have been committed after `go mod tidy` because that adds some
indirect dependencies in that example.
The revised `test-vendor` checks for that and (just in case that this
ever becomes desired) allows projects to not have a vendor directory
when using `go mod`.
How to use `go mod` properly gets documented in the README.md, because
there are such pitfalls.
This enables testing of other repos and of this repo itself inside
Prow. Currently supported is unit testing ("make test") and E2E
testing (either via a local test suite or the Kubernetes E2E test
suite applied to the hostpath driver example deployment).
The script passes shellcheck and uses Prow to verify that for future
PRs.
By default this only tests the scripts inside the "release-tools"
directory, which is useful when making experimental changes to them in
a component that uses csi-release-tools. But a component can also
enable checking for other directories.
