Add option to exclude devtools from fat jar

Add an `excludeDevtools` property to both the Maven and Gradle plugin
that removes `org.springframework.boot:spring-boot-devtools` (if
necessary) when repackaging the application.

Closes gh-3171

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/SpringBootPluginExtension.java

@@ -38,6 +38,7 @@ import org.springframework.boot.loader.tools.Layouts;
  *
  * @author Phillip Webb
  * @author Dave Syer
+ * @author Stephane Nicoll
  */
 public class SpringBootPluginExtension {
 
@@ -87,6 +88,11 @@ public class SpringBootPluginExtension {
 	 */
 	Set<String> requiresUnpack;
 
+	/**
+	 * Whether Spring Boot Devtools should be excluded from the fat jar.
+	 */
+	boolean excludeDevtools = false;
+
 	/**
 	 * Location of an agent jar to attach to the VM when running the application with
 	 * runJar task.
@@ -186,6 +192,14 @@ public class SpringBootPluginExtension {
 		this.requiresUnpack = requiresUnpack;
 	}
 
+	public boolean isExcludeDevtools() {
+		return this.excludeDevtools;
+	}
+
+	public void setExcludeDevtools(boolean excludeDevtools) {
+		this.excludeDevtools = excludeDevtools;
+	}
+
 	public File getAgent() {
 		return this.agent;
 	}

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/repackage/ProjectLibraries.java

@@ -155,12 +155,26 @@ class ProjectLibraries implements Libraries {
 		if (libraries != null) {
 			Set<String> duplicates = getDuplicates(libraries);
 			for (GradleLibrary library : libraries) {
-				library.setIncludeGroupName(duplicates.contains(library.getName()));
-				callback.library(library);
+				if (!isExcluded(library)) {
+					library.setIncludeGroupName(duplicates.contains(library.getName()));
+					callback.library(library);
+				}
 			}
 		}
 	}
 
+	private boolean isExcluded(GradleLibrary library) {
+		if (this.extension.isExcludeDevtools() && isDevToolsJar(library)) {
+			return true;
+		}
+		return false;
+	}
+
+	private boolean isDevToolsJar(GradleLibrary library) {
+		return "org.springframework.boot".equals(library.getGroup())
+				&& library.getName().startsWith("spring-boot-devtools");
+	}
+
 	private Set<String> getDuplicates(Set<GradleLibrary> libraries) {
 		Set<String> duplicates = new HashSet<String>();
 		Set<String> seen = new HashSet<String>();
@@ -187,6 +201,10 @@ class ProjectLibraries implements Libraries {
 			this.includeGroupName = includeGroupName;
 		}
 
+		public String getGroup() {
+			return this.group;
+		}
+
 		@Override
 		public String getName() {
 			String name = super.getName();