Add 'kubectl rabbitmq version' command (#450)

Relates #440

bin/kubectl-rabbitmq

@@ -66,11 +66,38 @@ USAGE:
 
   Print this help
     kubectl rabbitmq help
+
+  Print kubectl-rabbitmq plugin version
+    kubectl rabbitmq version
 END
 )
   echo "$usage"
 }
 
+version() {
+  # Since we require to install this plugin via krew, we get the version from krew instead of hardcoding a version to this file.
+  failure_msg="version cannot be determined because plugin was not installed via krew"
+  if ! command -v kubectl-krew &> /dev/null
+  then
+      echo "$failure_msg"
+      exit 1
+  fi
+
+  # We can't use `krew info` because it provides versions about available - not installed - plugins.
+  # `krew list` provides versions of installed plugins.
+  # We can't redirect stdout of `krew list` because this will suppress the version number (see `kubectl krew list --help`)
+  # Therefore, we have to get the version number from the `krew list` logs.
+  version_line=$(kubectl krew -v 4 list 2>&1 | grep 'rabbitmq: version=' || true)
+  if [[ -z "$version_line" ]];
+  then
+      echo "$failure_msg"
+      exit 1
+  fi
+
+  version="${version_line##*rabbitmq: version=}"
+  echo "kubectl-rabbitmq $version"
+}
+
 get_instance_details() {
     instance=${1}
     username=$(kubectl get secret "${instance}-default-user" -o jsonpath="{.data.username}" | base64 --decode)
@@ -305,6 +332,9 @@ main() {
     "-h")
         usage
         ;;
+    "version")
+        version
+        ;;
     *)
         usage
         exit 1

bin/kubectl-rabbitmq.bats

@@ -16,6 +16,20 @@ eventually() {
   return 1
 }
 
+@test "version outputs version" {
+  run kubectl rabbitmq version
+
+  if ! command -v kubectl-krew &> /dev/null
+  then
+    [ "$status" -eq 1 ]
+    [ "${lines[0]}" = "version cannot be determined because plugin was not installed via krew" ]
+  else
+    [ "$status" -eq 0 ]
+    version_regex='kubectl-rabbitmq v([0-9]+)\.([0-9]+)\.([0-9]+)$'
+    [[ "${lines[0]}" =~ $version_regex ]]
+  fi
+}
+
 @test "install-cluster-operator with too many args fails" {
   run kubectl rabbitmq install-cluster-operator too-many-args