RefSpec: reject refs ending in '/'

We had a case in Gerrits superproject subscriptions where
'refs/heads/' was configured with the intention to mean 'refs/heads/*'.

The first expression lacks the '*', which is why it is not considered
a wildcard but it was considered valid and so was not found early to be
a typo.

Refs are not allowed to end with '/' anyway, so add a check for that.

Change-Id: I3ffdd9002146382acafb4fbc310a64af4cc1b7a9
Signed-off-by: Stefan Beller <sbeller@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/RefSpecTest.java

 		assertEquals("foo/head", c.getSource());
 	}
 
+	@Test(expected = IllegalArgumentException.class)
+	public void invalidWhenSourceEndsWithSlash() {
+		assertNotNull(new RefSpec("refs/heads/"));
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void invalidWhenDestinationEndsWithSlash() {
+		assertNotNull(new RefSpec("refs/heads/master:refs/heads/"));
+	}
+
 	@Test(expected = IllegalArgumentException.class)
 	public void invalidWhenSourceOnlyAndWildcard() {
 		assertNotNull(new RefSpec("refs/heads/*"));

org.eclipse.jgit/src/org/eclipse/jgit/transport/RefSpec.java

 			return false;
 		if (s.contains("//")) //$NON-NLS-1$
 			return false;
+		if (s.endsWith("/")) //$NON-NLS-1$
+			return false;
 		int i = s.indexOf('*');
 		if (i != -1) {
 			if (s.indexOf('*', i + 1) > i)