Add support for @GrabExclude to AetherGrapeEngine

@GrabExclude can now be used to exclude certain transitive dependencies.
In Aether (Maven), exclusions are applied to an individual dependency
rather than being global. In Grape, exclusions are global.
AetherGrapeEngine adheres to the Grape convention by applying every
exclusion create by @GrabExclude to every dependency, effectively making
them global.

spring-boot-cli/src/test/java/org/springframework/boot/cli/compiler/grape/AetherGrapeEngineTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.cli.compiler.grape;
 
 import groovy.lang.GroovyClassLoader;
 
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -47,6 +48,20 @@ public class AetherGrapeEngineTests {
 		assertEquals(6, this.groovyClassLoader.getURLs().length);
 	}
 
+	@SuppressWarnings("unchecked")
+	@Test
+	public void dependencyResolutionWithExclusions() {
+		Map<String, Object> args = new HashMap<String, Object>();
+		args.put("excludes",
+				Arrays.asList(createExclusion("org.springframework", "spring-core")));
+
+		this.grapeEngine.grab(args,
+				createDependency("org.springframework", "spring-jdbc", "3.2.4.RELEASE"),
+				createDependency("org.springframework", "spring-beans", "3.2.4.RELEASE"));
+
+		assertEquals(4, this.groovyClassLoader.getURLs().length);
+	}
+
 	@Test
 	public void nonTransitiveDependencyResolution() {
 		Map<String, Object> args = new HashMap<String, Object>();
@@ -117,4 +132,11 @@ public class AetherGrapeEngineTests {
 		resolver.put("root", url);
 		return resolver;
 	}
+
+	private Map<String, Object> createExclusion(String group, String module) {
+		Map<String, Object> exclusion = new HashMap<String, Object>();
+		exclusion.put("group", group);
+		exclusion.put("module", module);
+		return exclusion;
+	}
 }