revision: parse parent in indegree_walk_step()

revision: parse parent in indegree_walk_step()

In indegree_walk_step(), we add unvisited parents to the indegree queue.
However, parents are not guaranteed to be parsed. As the indegree queue
sorts by generation number, let's parse parents before inserting them to
ensure the correct priority order.

Signed-off-by: Abhishek Kumar <redacted>
Reviewed-by: Taylor Blau <redacted>
Reviewed-by: Derrick Stolee <redacted>
Signed-off-by: Junio C Hamano <redacted>