Merge branch 'jk/subtree-do-not-push-if-split-fails'

"git subtree" (in contrib/) had one codepath with loose error
checks to lose data at the remote side.

* jk/subtree-do-not-push-if-split-fails:
  contrib/subtree: don't delete remote branches if split fails

contrib/subtree/git-subtree.sh

@@ -715,7 +715,8 @@ cmd_push()
 	    repository=$1
 	    refspec=$2
 	    echo "git push using: " $repository $refspec
-	    git push $repository $(git subtree split --prefix=$prefix):refs/heads/$refspec
+	    localrev=$(git subtree split --prefix="$prefix") || die
+	    git push $repository $localrev:refs/heads/$refspec
 	else
 	    die "'$dir' must already exist. Try 'git subtree add'."
 	fi