-# The upstream head must be given. Make sure it is valid.
-upstream_name="$1"
-upstream=`git rev-parse --verify "${upstream_name}^0"` ||
- die "invalid upstream $upstream_name"
+if test -z "$rebase_root"
+then
+ # The upstream head must be given. Make sure it is valid.
+ upstream_name="$1"
+ shift
+ upstream=`git rev-parse --verify "${upstream_name}^0"` ||
+ die "invalid upstream $upstream_name"
+ unset root_flag
+ upstream_arg="$upstream_name"
+else
+ test -z "$newbase" && die "--root must be used with --onto"
+ unset upstream_name
+ unset upstream
+ root_flag="--root"
+ upstream_arg="$root_flag"
+fi