Manifest: implement the Versioned interface

This migrates the version determination logic from VersionUtils
into the org.scijava.util.Manifest class directly.
And updates VersionUtils to lean on it.

Author: ctrueden

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

@@ -40,12 +40,14 @@
 import java.util.Map;
 import java.util.jar.Attributes;
 
+import org.scijava.Versioned;
+
 /**
  * Helper class for working with JAR manifests.
  * 
  * @author Curtis Rueden
  */
-public class Manifest {
+public class Manifest implements Versioned {
 
 	/** The JAR manifest backing this object. */
 	private final java.util.jar.Manifest manifest;
@@ -165,4 +167,24 @@ private static Manifest getManifest(final URL jarURL) throws IOException {
 		return new Manifest(conn.getManifest());
 	}
 
+	// -- Versioned methods --
+
+	@Override
+	public String getVersion() {
+		final String v = getBaseVersion();
+		if (v == null || !v.endsWith("-SNAPSHOT")) return v;
+
+		// append commit hash to differentiate between development versions
+		final String buildNumber = getImplementationBuild();
+		return buildNumber == null ? v : v + "-" + buildNumber;
+	}
+
+	// -- Helper methods --
+
+	private String getBaseVersion() {
+		final String manifestVersion = getImplementationVersion();
+		if (manifestVersion != null) return manifestVersion;
+		return getSpecificationVersion();
+	}
+
 }

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

@@ -80,13 +80,7 @@ public static String getVersion(final Class<?> c, final String groupId,
 	 */
 	public static String getVersionFromManifest(final Class<?> c) {
 		final Manifest m = Manifest.getManifest(c);
-		if (m == null) return null;
-		final String version = getVersionFromManifest(m);
-		if (version == null || !version.endsWith("-SNAPSHOT")) return version;
-
-		// append commit hash to differentiate between development versions
-		final String buildNumber = getBuildNumber(m);
-		return buildNumber == null ? version : version + "-" + buildNumber;
+		return m == null ? null : m.getVersion();
 	}
 
 	/**
@@ -115,18 +109,7 @@ public static String getVersionFromPOM(final Class<?> c,
 	 * @return Build number of specified {@link Class} or null if not found.
 	 */
 	public static String getBuildNumber(final Class<?> c) {
-		return getBuildNumber(Manifest.getManifest(c));
-	}
-
-	// -- Helper methods --
-
-	private static String getVersionFromManifest(final Manifest m) {
-		final String manifestVersion = m.getImplementationVersion();
-		if (manifestVersion != null) return manifestVersion;
-		return m.getSpecificationVersion();
-	}
-
-	private static String getBuildNumber(final Manifest m) {
+		final Manifest m = Manifest.getManifest(c);
 		return m == null ? null : m.getImplementationBuild();
 	}