Re: [PATCH 1/1] commit-graph: writing missing parents is a BUG

> From: Derrick Stolee <dstolee@microsoft.com>
>
> When writing a commit-graph, we write GRAPH_MISSING_PARENT if the
> parent's object id does not appear in the list of commits to be
> written into the commit-graph. This was done as the initial design
> allowed commits to have missing parents, but the final version
> requires the commit-graph to be closed under reachability. Thus,
> this GRAPH_MISSING_PARENT value should never be written.
>
> However, there are reasons why it could be written! These range
> from a bug in the reachable-closure code to a memory error causing
> the binary search into the list of object ids to fail. In either
> case, we should fail fast and avoid writing the commit-graph file
> with bad data.
>
> Remove the GRAPH_MISSING_PARENT constant in favor of the constant
> GRAPH_EDGE_LAST_MASK, which has the same value.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---