Require all projects to have a name

A project's name attribute is required according to repo's
doc/manifest-format.txt:

    <!ELEMENT project (annotation*,
                       project*)>
    <!ATTLIST project name        CDATA #REQUIRED>

Enforcing this in code makes reading easier (in particular making it
clearer that getName() and getPath() can never return null).

Change-Id: I8c7014dd6042183d7fecb2202af5acdc384aa8e4
Signed-off-by: Jonathan Nieder <jrn@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/ManifestParser.java

@@ -183,6 +183,9 @@ public class ManifestParser extends DefaultHandler {
 			String qName,
 			Attributes attributes) throws SAXException {
 		if ("project".equals(qName)) { //$NON-NLS-1$
+			if (attributes.getValue("name") == null) { //$NON-NLS-1$
+				throw new SAXException(RepoText.get().invalidManifest);
+			}
 			currentProject = new RepoProject(
 					attributes.getValue("name"), //$NON-NLS-1$
 					attributes.getValue("path"), //$NON-NLS-1$

org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/RepoProject.java

@@ -138,6 +138,9 @@ public class RepoProject implements Comparable<RepoProject> {
 	 */
 	public RepoProject(String name, String path, String revision,
 			String remote, String groups) {
+		if (name == null) {
+			throw new NullPointerException();
+		}
 		this.name = name;
 		if (path != null)
 			this.path = path;