rebase: avoid double reflog entry when switching branches

When switching a branch *and* updating said branch to a different
revision, let's avoid a double entry in HEAD's reflog by first updating
the branch and then adjusting the symbolic ref HEAD.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rebase.c

@@ -438,10 +438,11 @@ static int reset_head(struct object_id *oid, const char *action,
 				 detach_head ? REF_NO_DEREF : 0,
 				 UPDATE_REFS_MSG_ON_ERR);
 	else {
-		ret = create_symref("HEAD", switch_to_branch, msg.buf);
+		ret = update_ref(reflog_orig_head, switch_to_branch, oid,
+				 NULL, 0, UPDATE_REFS_MSG_ON_ERR);
 		if (!ret)
-			ret = update_ref(reflog_head, "HEAD", oid, NULL, 0,
-					 UPDATE_REFS_MSG_ON_ERR);
+			ret = create_symref("HEAD", switch_to_branch,
+					    reflog_head);
 	}
 
 leave_reset_head: