Add script command.

Also: prepare for execute-then-quit.
Add javadocs

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/Script.java

@@ -0,0 +1,58 @@
+package org.springframework.shell.standard.commands;
+
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.Reader;
+
+import org.jline.reader.Parser;
+import org.springframework.shell.Input;
+import org.springframework.shell.Shell;
+import org.springframework.shell.jline.FileInputProvider;
+import org.springframework.shell.standard.ShellComponent;
+import org.springframework.shell.standard.ShellMethod;
+
+/**
+ * A command that can read and execute other commands from a file.
+ *
+ * @author Eric Bottard
+ */
+@ShellComponent
+public class Script {
+
+    private final Shell shell;
+
+    private final Parser parser;
+
+    public Script(Shell shell, Parser parser) {
+        this.shell = shell;
+        this.parser = parser;
+    }
+
+    /**
+     * Marker interface for beans providing {@literal script} functionality to the shell.
+     * <p>
+     * <p>To override the script command, simply register your own bean implementing that interface
+     * and the standard implementation will back off.</p>
+     * <p>
+     * <p>To disable the {@literal script} command entirely, set the {@literal spring.shell.command.script.enabled=false}
+     * property in the environment.</p>
+     *
+     * @author Eric Bottard
+     */
+    public interface Command {
+    }
+
+    @ShellMethod(value = "Read and execute commands from a file")
+    public void script(File file) throws IOException {
+        Reader reader = new FileReader(file);
+        try (FileInputProvider inputProvider = new FileInputProvider(reader, parser)) {
+            Input input = inputProvider.readInput();
+            while (input != null) {
+                shell.evaluate(input);
+                input = inputProvider.readInput();
+            }
+        }
+    }
+
+}

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/StandardCommandsAutoConfiguration.java

@@ -18,6 +18,7 @@ package org.springframework.shell.standard.commands;
 
 import java.util.List;
 
+import org.jline.reader.Parser;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.context.annotation.Bean;
@@ -61,4 +62,10 @@ public class StandardCommandsAutoConfiguration {
 		return new Stacktrace();
 	}
 
+	@Bean
+	@ConditionalOnMissingBean(Script.Command.class)
+	@ConditionalOnProperty(prefix = "spring.shell.command.script", value = "enabled", havingValue = "true", matchIfMissing = true)
+	public Script script(Shell shell, Parser parser) {
+		return new Script(shell, parser);
+	}
 }