Align with Buildship 3.0's API

Previously, the plugin was incorrectly using Buildship 3.1 API while
claiming compatibility with 3.0. This could lead to NoSuchMethodErrors
at runtime.

This commit updates the code to use Buildship 3.0 API. It also
updates the manifest to constrain the version of the
org.eclipse.buildship.core bundle to 3.0.x versions. Lastly, the
Eclipse repository that is used has been rolled back to 2019-03
as 2019-06 bundles Buildship 3.1.

Closes gh-121

Author: wilkinsona

Diff for: pom.xml

@@ -31,7 +31,7 @@
 		<main.basedir>${basedir}</main.basedir>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<java.version>1.8</java.version>
-		<eclipse.repository>https://download.eclipse.org/releases/2019-06/201906191000</eclipse.repository>
+		<eclipse.repository>https://download.eclipse.org/releases/2019-03/201903201000</eclipse.repository>
 		<eclipse.checkstyle.repository>https://dl.bintray.com/eclipse-cs/eclipse-cs/8.18.0</eclipse.checkstyle.repository>
 		<tycho.disableP2Mirrors>true</tycho.disableP2Mirrors>
 		<ant.version>1.8.1</ant.version>

Diff for: spring-javaformat-eclipse/io.spring.javaformat.eclipse/META-INF/MANIFEST.MF

@@ -16,7 +16,7 @@ Require-Bundle: org.eclipse.ui,
  org.eclipse.m2e.jdt;resolution:=optional,
  org.eclipse.m2e.core;resolution:=optional,
  org.eclipse.m2e.maven.runtime;resolution:=optional,
- org.eclipse.buildship.core;bundle-version="3.0.0";resolution:=optional,
+ org.eclipse.buildship.core;bundle-version="[3.0.0,3.1.0)";resolution:=optional,
  net.sf.eclipsecs.core;bundle-version="8.18.0";resolution:=optional
 Bundle-ClassPath: .,
  lib/spring-javaformat-formatter-eclipse.jar,

Diff for: spring-javaformat-eclipse/io.spring.javaformat.eclipse/src/io/spring/javaformat/eclipse/gradle/RefreshProjectsSettingsJob.java

@@ -26,8 +26,10 @@
 
 import org.eclipse.buildship.core.GradleBuild;
 import org.eclipse.buildship.core.internal.CorePlugin;
+import org.eclipse.buildship.core.internal.workspace.FetchStrategy;
 import org.eclipse.buildship.core.internal.workspace.InternalGradleBuild;
 import org.eclipse.buildship.core.internal.workspace.InternalGradleWorkspace;
+import org.eclipse.buildship.core.internal.workspace.ModelProviderUtil;
 import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.core.runtime.CoreException;
@@ -97,15 +99,15 @@ private void configureProjects(IProgressMonitor monitor) throws CoreException, I
 
 	private void configureProject(IProject project, InternalGradleBuild build, IProgressMonitor monitor)
 			throws CoreException, IOException {
-		Collection<EclipseProject> projects = build.getModelProvider()
-				.fetchEclipseProjectAndRunSyncTasks(this.tokenSource, monitor);
+		Set<EclipseProject> projects = ModelProviderUtil.fetchAllEclipseProjects(build, this.tokenSource,
+				FetchStrategy.FORCE_RELOAD, monitor);
 		if (hasSpringFormatPlugin(projects)) {
 			ProjectSettingsFilesLocator locator = new ProjectSettingsFilesLocator(getSearchFolders(projects));
 			locator.locateSettingsFiles().applyToProject(project, monitor);
 		}
 	}
 
-	private boolean hasSpringFormatPlugin(Collection<EclipseProject> projects) {
+	private boolean hasSpringFormatPlugin(Set<EclipseProject> projects) {
 		for (EclipseProject project : projects) {
 			for (GradleTask task : project.getGradleProject().getTasks()) {
 				if (isSpringFormatPlugin(task)) {
@@ -120,7 +122,7 @@ private boolean isSpringFormatPlugin(GradleTask task) {
 		return TASK_NAME.equals(task.getName());
 	}
 
-	private Set<File> getSearchFolders(Collection<EclipseProject> projects) {
+	private Set<File> getSearchFolders(Set<EclipseProject> projects) {
 		Set<File> searchFolders = new LinkedHashSet<>();
 		for (EclipseProject project : projects) {
 			while (project != null) {