VersionUtils.compare: handle SemVer suffixes

With SemVer, 2.0.0 is newer than 2.0.0-beta-1.
We were behaving in the opposite way.

In other words: we want empty post-numeric suffixes to sort _after_
non-empty ones. So we need a special test for empty string here.

Author: ctrueden

src/main/java/org/scijava/util/VersionUtils.java

@@ -156,6 +156,13 @@ private static int compareToken(final String t1, final String t2) {
 			suffix1 = t1.substring(i1);
 			suffix2 = t2.substring(i2);
 		}
+
+		// Final version (empty string) is larger than non-final (non-empty).
+		// For example: 2.0.0 > 2.0.0-beta-1.
+		if (suffix1.isEmpty() && suffix2.isEmpty()) return 0;
+		if (suffix1.isEmpty()) return 1;
+		if (suffix2.isEmpty()) return -1;
+
 		// Compare lexicographically.
 		return suffix1.compareTo(suffix2);
 	}

src/test/java/org/scijava/util/VersionUtilsTest.java

@@ -60,7 +60,7 @@ public void testCompare() {
 		assertTrue(VersionUtils.compare("2.7.3", "1.7.3") > 0);
 
 		// Suffix indicates version is older than final release.
-		assertTrue(VersionUtils.compare("1.5.2", "1.5.2-beta-1") < 0);
+		assertTrue(VersionUtils.compare("1.5.2", "1.5.2-beta-1") > 0);
 
 		// Check when number of version tokens does not match.
 		assertTrue(VersionUtils.compare("1.5", "1.5.1") < 0);