Branch normalizer should not normalize already valid branch names

Change-Id: Ib746655e32a37c4ad323f1d12ac0817de8fa56cf
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ValidRefNameTest.java

@@ -329,4 +329,18 @@ public class ValidRefNameTest {
 				Repository.normalizeBranchName("Bug 1#$  2345 - Hello World")
 						.equals("Bug_12345-Hello_World"));
 	}
+
+	@Test
+	public void testNormalizeAlreadyValidRefName() {
+		assertEquals(true,
+				Repository.normalizeBranchName("refs/heads/m.a.s.t.e.r")
+						.equals("refs/heads/m.a.s.t.e.r"));
+	}
+
+	@Test
+	public void testNormalizeTrimmedUnicodeAlreadyValidRefName() {
+		assertEquals(true,
+				Repository.normalizeBranchName(" \u00e5ngstr\u00f6m\t")
+						.equals("\u00e5ngstr\u00f6m"));
+	}
 }

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

@@ -1898,11 +1898,12 @@ public abstract class Repository implements AutoCloseable {
 	 * Future implementations of this method could be more restrictive or more
 	 * lenient about the validity of specific characters in the returned name.
 	 * <p/>
-	 * The current implementation returns a trimmed string only containing word
-	 * characters ([a-zA-Z_0-9]) and hyphens ('-'). Colons are replaced by
-	 * hyphens. Repeating underscores and hyphens are replaced by a single
-	 * occurrence. Underscores and hyphens at the beginning of the string are
-	 * removed.
+	 * The current implementation returns the trimmed input string if this is
+	 * already a valid branch name. Otherwise it returns a trimmed string only
+	 * containing word characters ([a-zA-Z_0-9]) and hyphens ('-'). Colons are
+	 * replaced by hyphens. Repeating underscores and hyphens are replaced by a
+	 * single occurrence. Underscores and hyphens at the beginning of the string
+	 * are removed.
 	 *
 	 * @param name
 	 *            The name to normalize.
@@ -1916,6 +1917,11 @@ public abstract class Repository implements AutoCloseable {
 			return name;
 		}
 		String result = name.trim();
+		String fullName = result.startsWith(Constants.R_HEADS) ? result
+				: Constants.R_HEADS + result;
+		if (isValidRefName(fullName)) {
+			return result;
+		}
 		return result.replaceAll("\\s+([_:-])*?\\s+", "$1") //$NON-NLS-1$//$NON-NLS-2$
 				.replaceAll(":", "-") //$NON-NLS-1$//$NON-NLS-2$
 				.replaceAll("\\s+", "_") //$NON-NLS-1$//$NON-NLS-2$