Let RepositoryBuilder find bare repos

BaseRepositoryBuilder.findGitDir() was not searching correctly for bare
repositories. E.g. when running org.eclipse.jgit.pgm.Log and the current
directory was that of a bare git repository an error "fatal: error:
can't find git directory" was raised. With this fix RepositoryBuilder
will also check whether the given directory is the root of a bare
repository.

Bug: 450193
Change-Id: I4d4ad42e24ca397745adb0f3385caee3bcf3a186
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/BaseRepositoryBuilder.java

@@ -514,13 +514,17 @@ public class BaseRepositoryBuilder<B extends BaseRepositoryBuilder, R extends Re
 				if (FileKey.isGitRepository(dir, tryFS)) {
 					setGitDir(dir);
 					break;
-				} else if (dir.isFile())
+				} else if (dir.isFile()) {
 					try {
 						setGitDir(getSymRef(current, dir, tryFS));
 						break;
 					} catch (IOException ignored) {
 						// Continue searching if gitdir ref isn't found
 					}
+				} else if (FileKey.isGitRepository(current, tryFS)) {
+					setGitDir(current);
+					break;
+				}
 
 				current = current.getParentFile();
 				if (current != null && ceilingDirectories != null