Remove UTF-8 checking duplication in Config lib subclasses

Change-Id: Ib9f0ae8207000a36c5bf1a92fcc2c32efc4c0984
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/BlobBasedConfig.java

@@ -80,8 +80,7 @@ public class BlobBasedConfig extends Config {
 			throws ConfigInvalidException {
 		super(base);
 		final String decoded;
-		if (blob.length >= 3 && blob[0] == (byte) 0xEF
-				&& blob[1] == (byte) 0xBB && blob[2] == (byte) 0xBF) {
+		if (isUtf8(blob)) {
 			decoded = RawParseUtils.decode(RawParseUtils.UTF8_CHARSET,
 					blob, 3, blob.length);
 		} else {

org.eclipse.jgit/src/org/eclipse/jgit/lib/Config.java

@@ -1108,6 +1108,19 @@ public class Config {
 		state.set(newState());
 	}
 
+	/**
+	 * Check if bytes should be treated as UTF-8 or not.
+	 *
+	 * @param bytes
+	 *            the bytes to check encoding for.
+	 * @return true if bytes should be treated as UTF-8, false otherwise.
+	 * @since 4.4
+	 */
+	protected boolean isUtf8(final byte[] bytes) {
+		return bytes.length >= 3 && bytes[0] == (byte) 0xEF
+				&& bytes[1] == (byte) 0xBB && bytes[2] == (byte) 0xBF;
+	}
+
 	private static String readSectionName(final StringReader in)
 			throws ConfigInvalidException {
 		final StringBuilder name = new StringBuilder();

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/FileBasedConfig.java

@@ -147,8 +147,7 @@ public class FileBasedConfig extends StoredConfig {
 					snapshot = newSnapshot;
 			} else {
 				final String decoded;
-				if (in.length >= 3 && in[0] == (byte) 0xEF
-						&& in[1] == (byte) 0xBB && in[2] == (byte) 0xBF) {
+				if (isUtf8(in)) {
 					decoded = RawParseUtils.decode(RawParseUtils.UTF8_CHARSET,
 							in, 3, in.length);
 					utf8Bom = true;