Prepare CLI for extension sunsetting (#825)

Author: philipp-spiess

cmd/src/extensions.go

@@ -10,7 +10,8 @@ var extensionsCommands commander
 func init() {
 	usage := `'src extensions' is a tool that manages extensions in the extension registry on a Sourcegraph instance.
 
-EXPERIMENTAL: Extensions are experimental functionality on Sourcegraph and in the 'src' tool.
+DEPRECATED: We're in the process of removing Sourcegraph extensions with our September release.
+            Learn more: https://docs.sourcegraph.com/extensions/deprecation
 
 Usage:
 

cmd/src/extensions_list.go

@@ -63,6 +63,7 @@ Examples:
       nodes {
         ...RegistryExtensionFields
       }
+      error
     }
   }
 }` + registryExtensionFragment
@@ -71,6 +72,7 @@ Examples:
 			ExtensionRegistry struct {
 				Extensions struct {
 					Nodes []Extension
+					Error string
 				}
 			}
 		}
@@ -81,6 +83,10 @@ Examples:
 			return err
 		}
 
+		if result.ExtensionRegistry.Extensions.Error != "" {
+			return fmt.Errorf("%s", result.ExtensionRegistry.Extensions.Error)
+		}
+
 		for _, extension := range result.ExtensionRegistry.Extensions.Nodes {
 			if err := execTemplate(tmpl, extension); err != nil {
 				return err