Mention all changes for GA releases on GitHub release page.

Closes #70

Author: christophstrobl

Diff for: src/main/java/org/springframework/data/release/git/GitOperations.java

@@ -436,7 +436,7 @@ public TrainIteration getPreviousIteration(TrainIteration trainIteration) {
 
 		Assert.notNull(trainIteration, "TrainIteration must not be null!");
 
-		if (trainIteration.getIteration().isMilestone() && trainIteration.getIteration().getIterationValue() == 1) {
+		if (isGaOrFirstMilestone(trainIteration.getIteration())) {
 
 			Train trainToUse = getPreviousTrain(trainIteration);
 			return trainToUse.getIteration(Iteration.GA);
@@ -546,6 +546,10 @@ private static Train getPreviousTrain(TrainIteration trainIteration) {
 		return trainToUse;
 	}
 
+	private static boolean isGaOrFirstMilestone(Iteration iteration) {
+		return iteration.isGAIteration() || (iteration.isMilestone() && iteration.getIterationValue() == 1);
+	}
+
 	private Stream<Branch> getRemoteBranches(Project project) {
 
 		return doWithGit(project, git -> {

Diff for: src/test/java/org/springframework/data/release/git/GitOperationsIntegrationTests.java

@@ -84,8 +84,8 @@ void shouldDeterminePreviousIterationFromGA() throws Exception {
 
 		TrainIteration hopperRc1 = gitOperations.getPreviousIteration(ReleaseTrains.HOPPER.getIteration(Iteration.GA));
 
-		assertThat(hopperRc1.getTrain()).isEqualTo(ReleaseTrains.HOPPER);
-		assertThat(hopperRc1.getIteration()).isEqualTo(Iteration.RC1);
+		assertThat(hopperRc1.getTrain()).isEqualTo(ReleaseTrains.GOSLING);
+		assertThat(hopperRc1.getIteration()).isEqualTo(Iteration.GA);
 
 		TrainIteration hopperM1 = gitOperations.getPreviousIteration(ReleaseTrains.HOPPER.getIteration(Iteration.RC1));