This script handles the necessary "replace" statements and determines
which packages need to be updated in lockstep.

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.

build.make: allow repos to use 'go mod' for vendoring

How a repo does vendoring is detected based on the presence of
Gopkg.toml.

The vendor check with `dep` was all done locally, but the
corresponding check for `go mod` requires network access. The check
therefore gets skipped when running in the Prow CI in situations where
we are sure that it isn't needed (for example, in a periodic job).

update to Go 1.12.4

Kubernetes also requires 1.12. We pick the latest stable release
for CI builds.

prow.sh: skip sanity testing if component doesn't support it

Whether a component supports sanity testing depends on the
component. For example, csi-driver-host-path enables it because it
makes sense there (and only there). Letting the prow.sh script decide
whether it actually runs simplifies the job definitions in test-infra.

prow.sh: update csi-driver-host-path

This pulls in
https://github.com/kubernetes-csi/csi-driver-host-path/pull/37, which
turned out to be necessary for pre-submit testing of the
livenessprobe.

build.make: Replace 'return' to 'exit' to fix shellcheck error

prow.sh: remove AllAlpha=all, part II

This was already meant to be done earlier in cda2fc58.
While at it, extend the permanent TODO with guidance on future feature
gates.

prow enhancements

It turned out to not work. Instead of reverting the commit which
introduced this, let's better document this explicitly.

When KinD fails in a Prow job, we need additional information to
understand why it failed.

Not all environments have Docker. The simplifying assumption here is
that if the Docker command is available, it's also usable.

When running only some tests, sometimes extra, unnecessarily work was
done, like bringing up the cluster without alpha gates.

The previous logic failed for canary jobs, those also deploy a recent
driver. Instead of guessing what driver gets installed based on job
parameters, check what really runs in the cluster and base the
decision on that.

We only need to maintain this blacklist for 1.0.x until we replace it
with 1.1.0, then this entire hostpath_supports_block can be removed.

"grep -w" treated "serial-alpha" as two words and therefore
CSI_PROW_TESTS sometimes ran too many tests.

This ensures that also new, currently unknown alpha gates are enabled
when testing against a future Kubernetes versions. For all currently
known Kubernetes versions we just use the minimal set of alpha gates,
which ensures that we don't miss any of them in our documentation.

Prow testing

The temporary fork was merged, we can use the upstream repo again.

Instead of always using the latest E2E tests for all Kubernetes
versions, the plan now is to use the tests that match the Kubernetes
version. However, for 1.13 we have to make an exception because the
suite for that version did not support the necessary
--storage.testdriver parameter.

While switching back and forth between release-1.13 and release-1.14
locally, there was the problem that the local kind image kept using
the wrong kubelet binary despite rebuilding from source. The problem
went away after cleaning the Bazel cache. Exact root cause unknown,
but perhaps using unique tags and properly cleaning the repo helps.

If not, then the unique tags at least will show what the problem is.

Using the same (recent) Go version for all Kubernetes versions can
break for older versions when there are incompatible changes in Go. To
avoid that, we use exactly the minimum version of Go required for each
Kubernetes version. This is based on the assumption that this
combination was tested successfully.

When building the E2E suite from Kubernetes (the default) we do the
same, but still allow building it from elsewhere.

We allow the Go version to be empty when it doesn't matter.

The travis.yml is now the only place where the Go version for the
component itself needs to be configured.

verify shellcheck

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.

These are the modifications that were necessary to call this outside
of Kubernetes. The support for excluding files from checking gets
removed to simplify the script. It shouldn't be needed, because
linting can be enabled after fixing whatever scripts might fail the
check.

build.make: avoid unit-testing E2E test suite

In repos that have a test/e2e, that test suite should be run
separately because it depends on a running cluster.

check vendor directory

This runs "dep check" to verify that the vendor directory is
up-to-date and meets expectations (= done with dep >= 0.5.0).

This is an unmodified copy of kubernetes/hack/verify-shellcheck.sh
revision d5a3db003916b1d33b503ccd2e4897e094d8af77.

In repos that have a test/e2e, that test suite should be run
separately because it depends on a running cluster.

verify-subtree.sh: relax check and ignore old content