Ensure .gitmodules is loaded when accessing submodule name

This problem occurred when calling SubmoduleWalk#getModuleName if the
first submodule processed has a name and a path which do not match
SubmoduleWalk#getModuleName returned the module path instead of the
module name. In order to fix this SubmoduleWalk#getModuleName needs to
ensure that the modules config is loaded.

Bug: 565776
Change-Id: I36ce1fbc64c4849f9d8e39864b825c6e28d344f8
Signed-off-by: John Dallaway <john@dallaway.org.uk>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/submodule/SubmoduleWalkTest.java

 		final CanonicalTreeParser p = new CanonicalTreeParser();
 		p.reset(testDb.getRevWalk().getObjectReader(), commit.getTree());
 		try (SubmoduleWalk gen = SubmoduleWalk.forPath(db, p, "sub")) {
+			assertEquals(arbitraryName, gen.getModuleName());
 			assertEquals(path, gen.getPath());
 			assertEquals(subId, gen.getObjectId());
 			assertEquals(new File(db.getWorkTree(), path), gen.getDirectory());

org.eclipse.jgit/src/org/eclipse/jgit/api/SubmoduleDeinitCommand.java

 import java.util.List;
 
 import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.api.errors.InvalidConfigurationException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
 import org.eclipse.jgit.api.errors.NoHeadException;
+import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.ObjectId;
 				}
 			}
 			return results;
+		} catch (ConfigInvalidException e) {
+			throw new InvalidConfigurationException(e.getMessage(), e);
 		} catch (IOException e) {
 			throw new JGitInternalException(e.getMessage(), e);
 		}

org.eclipse.jgit/src/org/eclipse/jgit/submodule/SubmoduleWalk.java

 	 *
 	 * @since 4.10
 	 * @return name
+	 * @throws ConfigInvalidException
+	 * @throws IOException
 	 */
-	public String getModuleName() {
+	public String getModuleName() throws IOException, ConfigInvalidException {
+		lazyLoadModulesConfig();
 		return getModuleName(path);
 	}