add maven support

Author: abelk2

lib/src/main/java/com/diffplug/spotless/generic/LicenseHeaderStep.java

@@ -108,7 +108,7 @@ public LicenseHeaderStep withYearModeLazy(Supplier<YearMode> yearMode) {
 		return new LicenseHeaderStep(name, contentPattern, headerLazy, delimiter, yearSeparator, yearMode, skipLinesMatching);
 	}
 
-	public LicenseHeaderStep withSkipLinesMatching(String skipLinesMatching) {
+	public LicenseHeaderStep withSkipLinesMatching(@Nullable String skipLinesMatching) {
 		return new LicenseHeaderStep(name, contentPattern, headerLazy, delimiter, yearSeparator, yearMode, skipLinesMatching);
 	}
 

plugin-maven/src/main/java/com/diffplug/spotless/maven/generic/LicenseHeader.java

@@ -37,6 +37,9 @@ public class LicenseHeader implements FormatterStepFactory {
 	@Parameter
 	private String delimiter;
 
+	@Parameter
+	private String skipLinesMatching;
+
 	@Override
 	public final FormatterStep newFormatterStep(FormatterStepConfig config) {
 		String delimiterString = delimiter != null ? delimiter : config.getLicenseHeaderDelimiter();
@@ -53,6 +56,7 @@ public final FormatterStep newFormatterStep(FormatterStepConfig config) {
 			}
 			return LicenseHeaderStep.headerDelimiter(() -> readFileOrContent(config), delimiterString)
 					.withYearMode(yearMode)
+					.withSkipLinesMatching(skipLinesMatching)
 					.build()
 					.filterByFile(LicenseHeaderStep.unsupportedJvmFilesFilter());
 		} else {