in src/main/java/org/apache/maven/plugin/compiler/CompilerMojo.java [365:375]
protected SourceInclusionScanner getSourceInclusionScanner(String inputFileEnding) {
// it's not defined if we get the ending with or without the dot '.'
String defaultIncludePattern = "**/*" + (inputFileEnding.startsWith(".") ? "" : ".") + inputFileEnding;
if (includes.isEmpty()) {
includes.add(defaultIncludePattern);
}
Set<String> excludesIncr = new HashSet<>(excludes);
excludesIncr.addAll(excludesIncr);
return new SimpleSourceInclusionScanner(includes, excludesIncr);
}