Remove sorting in the main path

It doesn't seem important that the file is sorted, and the output of
DeltaList is only sorted if we choose to display it.

Related to #334

Author: gsmet

src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java

@@ -1851,10 +1851,8 @@ private boolean hasInputFileTreeChanged(IncrementalBuildHelper ibh, Set<File> in
             }
         }
 
-        Set<String> newInputFiles = inputFiles.stream()
-                .sorted()
-                .map(File::getAbsolutePath)
-                .collect(Collectors.toCollection(LinkedHashSet::new));
+        Set<String> newInputFiles =
+                inputFiles.stream().map(File::getAbsolutePath).collect(Collectors.toCollection(HashSet::new));
 
         try {
             Files.write(mojoConfigFile, newInputFiles);
@@ -1866,10 +1864,13 @@ private boolean hasInputFileTreeChanged(IncrementalBuildHelper ibh, Set<File> in
 
         DeltaList<String> inputTreeChanges = new DeltaList<>(oldInputFiles, newInputFiles);
         if (getLog().isDebugEnabled() || showCompilationChanges) {
-            for (String fileAdded : inputTreeChanges.getAdded()) {
+            // we only sort the output when pushed to the user
+            for (String fileAdded :
+                    inputTreeChanges.getAdded().stream().sorted().collect(Collectors.toList())) {
                 getLog().info("\tInput tree files (+): " + fileAdded);
             }
-            for (String fileRemoved : inputTreeChanges.getRemoved()) {
+            for (String fileRemoved :
+                    inputTreeChanges.getRemoved().stream().sorted().collect(Collectors.toList())) {
                 getLog().info("\tInput tree files (-): " + fileRemoved);
             }
         }

src/main/java/org/apache/maven/plugin/compiler/DeltaList.java

@@ -33,9 +33,8 @@ final class DeltaList<E> {
     private final boolean hasChanged;
 
     DeltaList(Collection<E> oldList, Collection<E> newList) {
-        this.added = newList.stream().filter(i -> !oldList.contains(i)).sorted().collect(Collectors.toList());
-        this.removed =
-                oldList.stream().filter(i -> !newList.contains(i)).sorted().collect(Collectors.toList());
+        this.added = newList.stream().filter(i -> !oldList.contains(i)).collect(Collectors.toList());
+        this.removed = oldList.stream().filter(i -> !newList.contains(i)).collect(Collectors.toList());
         this.hasChanged = !added.isEmpty() || !removed.isEmpty();
     }