golangci-lint: enable running specific linters

To run just a specific linter based on command line flags, the default
configuration needs to be disabled (because it would enable additional ones)
and then command line flags must be passed through to "golangci-lint run".

For example, to lint with just "go vet" in verbose mode, use:

    verify-golangci-lint.sh -c none -- --disable-all --enable=govet -v

hack/verify-golangci-lint.sh

@@ -16,7 +16,16 @@
 
 # This script checks coding style for go language files in each
 # Kubernetes package by golint.
-# Usage: `hack/verify-golangci-lint.sh`.
+
+usage () {
+  cat <<EOF >&2
+Usage: $0 [-- <golangci-lint run flags>] [packages]"
+   -c <config|"none">: use the specified configuration or none instead of the default hack/golangci.yaml
+   [packages]: check specific packages or directories instead of everything
+EOF
+  exit 1
+}
+
 
 set -o errexit
 set -o nounset
@@ -41,7 +50,35 @@ invocation=(./hack/verify-golangci-lint.sh "$@")
 # _output/local/bin/golangci-lint cache clean
 golangci=(env LOGCHECK_CONFIG="${KUBE_ROOT}/hack/logcheck.conf" "${GOBIN}/golangci-lint" run)
 golangci_config="${KUBE_ROOT}/hack/golangci.yaml"
+while getopts "c:" o; do
+  case "${o}" in
+    c)
+      if [ "${OPTARG}" = "none" ]; then
+        golangci_config=""
+      else
+        golangci_config="${OPTARG}"
+      fi
+      ;;
+   *)
+     usage
+     ;;
+  esac
+done
+
+if [ "${golangci_config}" ]; then
     golangci+=(--config="${golangci_config}")
+fi
+
+# Filter out arguments that start with "-" and move them to the run flags.
+shift $((OPTIND-1))
+targets=()
+for arg; do
+  if [[ "${arg}" == -* ]]; then
+    golangci+=("${arg}")
+  else
+    targets+=("${arg}")
+  fi
+done
 
 kube::golang::verify_go_version
 
@@ -52,15 +89,18 @@ export GO111MODULE=on
 echo "installing golangci-lint and logcheck plugin from hack/tools into ${GOBIN}"
 pushd "${KUBE_ROOT}/hack/tools" >/dev/null
   go install github.com/golangci/golangci-lint/cmd/golangci-lint
+  if [ "${golangci_config}" ]; then
+    # This cannot be used without a config.
     go build -o "${GOBIN}/logcheck.so" -buildmode=plugin sigs.k8s.io/logtools/logcheck/plugin
+  fi
 popd >/dev/null
 
 cd "${KUBE_ROOT}"
 
 res=0
-if [[ "$#" -gt 0 ]]; then
-    echo "running ${golangci[*]} $*" >&2
-    "${golangci[@]}" "$@" >&2 || res=$?
+if [[ "${#targets[@]}" -gt 0 ]]; then
+    echo "running ${golangci[*]} ${targets[*]}" >&2
+    "${golangci[@]}" "${targets[@]}" >&2 || res=$?
 else
     echo "running ${golangci[*]} ./..." >&2
     "${golangci[@]}" ./... >&2 || res=$?