Function forest_filecoin::rpc::methods::chain::impl_chain_get_path

fn impl_chain_get_path(
    chain_store: &ChainStore<impl Blockstore>,
    from: &TipsetKey,
    to: &TipsetKey,
) -> Result<Vec<PathChange>>

Find the path between two tipsets, as a series of PathChanges.

0 - A - B - C - D
    ^~~~~~~~> apply B, C

0 - A - B - C - D
    <~~~~~~~^ revert C, B

    <~~~~~~~~ revert C, B
0 - A - B  - C
    |
     -- B' - C'
     ~~~~~~~~> then apply B', C'

Exposes errors from the Blockstore, and returns an error if there is no common ancestor.