feat(anc): add check-hotfix subcommand to read hotfix pointer from ConfigMap

aks-node-controller/app.go

@@ -43,11 +43,18 @@ type App struct {
 	eventLogger *helpers.EventLogger
 
 	// hotfixVersionPath overrides the default hotfix version file location for testing.
+	// It is also the path check-hotfix writes the resolved pointer to.
 	hotfixVersionPath string
 	// aptSourcesDir overrides the default APT sources directory for testing.
 	aptSourcesDir string
 	// nodeCustomDataPath overrides the default nodecustomdata path for testing.
 	nodeCustomDataPath string
+	// nodeConfigPath overrides the default AKSNodeConfig path for testing. It is the
+	// source for check-hotfix's apiserver credentials and cold-start fallback pointer.
+	nodeConfigPath string
+	// checkHotfixConfigMapFetcher overrides the real apiserver ConfigMap GET for testing,
+	// letting unit tests inject canned ConfigMap JSON or errors without real networking.
+	checkHotfixConfigMapFetcher func(ctx context.Context) ([]byte, error)
 }
 
 // provision.json values are emitted as strings by the shell jq invocation.
@@ -137,6 +144,16 @@ func (a *App) Run(ctx context.Context, args []string) int {
 					return a.runDownloadHotfixCommand(ctx)
 				},
 			},
+			{
+				Name:  "check-hotfix",
+				Usage: "Read the anc-hotfix-version ConfigMap and stage the hotfix pointer (fail-open)",
+				Action: func(ctx context.Context, cmd *cli.Command) error {
+					if len(cmd.Args().Slice()) > 0 {
+						return fmt.Errorf("unexpected check-hotfix arguments: %s", strings.Join(cmd.Args().Slice(), " "))
+					}
+					return a.runCheckHotfixCommand(ctx)
+				},
+			},
 		},
 	}