Allow InitCommand to run on existing git repos

To be more consistent with what native git does we should allow
to run the InitCommand also on existing git repos.

Change-Id: I833637842631b37dce96ed9729b3a6ed24054056
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

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

@@ -52,7 +52,7 @@ import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.RepositoryBuilder;
 
 /**
- * Create an empty git repository
+ * Create an empty git repository or reinitalize an existing one
  *
  * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-init.html"
  *      >Git documentation about init</a>
@@ -89,6 +89,7 @@ public class InitCommand implements Callable<Git> {
 				builder.setGitDir(d);
 			}
 			Repository repository = builder.build();
+			if (!repository.getObjectDatabase().exists())
 				repository.create(bare);
 			return new Git(repository);
 		} catch (IOException e) {