Make RepoProject#setUpstream public

Applications using JGit such as Gerrit plugins may have their own
manifest parsers. They can start using RepoProject to some extent
with this change. Eventually, they can be migrated to use the
ManifestParser in JGit, however until then, this change can help
make the migration incremental.

Change-Id: I6a32d4f4622c3842eedf7873cdfed2f1ca998f6f
(cherry picked from commit e3e0a1ea35a27e50e0280715a417be7d69fa3345)

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

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/RepoProject.java b/org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/RepoProject.java
index aa1af21..3ed0bef 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/RepoProject.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/gitrepo/RepoProject.java
@@ -411,7 +411,7 @@ public String getUpstream() {
 	 *
 	 * @since 6.10
 	 */
-	void setUpstream(String upstream) {
+	public void setUpstream(String upstream) {
 		this.upstream = upstream;
 	}