Fixed completion only for particular command option (#1246)

[czpilar]

Resolves #1246

[fmbenhassine]

LGTM 👍 Works with multiple options as well:

package org.springframework.shell.samples.helloworld.boot;

import java.util.Collections;
import java.util.stream.Stream;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.shell.core.command.CommandOption;
import org.springframework.shell.core.command.annotation.Command;
import org.springframework.shell.core.command.annotation.Option;
import org.springframework.shell.core.command.completion.CompletionProposal;
import org.springframework.shell.core.command.completion.CompletionProvider;

@SpringBootApplication
public class SpringShellApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringShellApplication.class, args);
	}

	@Command(name = "hello", completionProvider = "helloNameCompletionProvider")
	public void sayHello(@Option(longName = "firstName", shortName = 'f') String firstName,
			@Option(longName = "lastName", shortName = 'l') String lastName) {
		System.out.println("Hello " + firstName + " " + lastName + "!");
	}

	@Bean
	public CompletionProvider helloNameCompletionProvider() {
		return completionContext -> {
			CommandOption option = completionContext.getCommandOption();
			if (option == null) {
				return Collections.emptyList();
			}
			if ("firstName".equals(option.longName()) || 'f' == option.shortName()) {
				return Stream.of("Foo1", "Foo2").map(CompletionProposal::new).toList();
			}
			if ("lastName".equals(option.longName()) || 'l' == option.shortName()) {
				return Stream.of("Bar1", "Bar2").map(CompletionProposal::new).toList();
			}
			return Collections.emptyList();
		};
	}

}

Completion works as expected in this example. Thank you for the PR!

[fmbenhassine]

Rebased, squashed and merged as 1d91365.

Thank you for yet another awesome contribution! 🙏