Possible documentation inaccuracy in optimizer README

Hello,

In https://github.com/postgres/postgres/tree/master/src/backend/optimizer, there are two examples on the dynamic programming (DP) algorithm used in the optimizer, which I think 

have some inaccuracy:

SELECT  *    FROM    tab1, tab2, tab3, tab4    WHERE   tab1.col = tab2.col AND        tab2.col = tab3.col AND        tab3.col = tab4.col
    Tables 1, 2, 3, and 4 are joined as:    {1 2},{2 3},{3 4}    {1 2 3},{2 3 4}    {1 2 3 4}    (other possibilities will be excluded for lack of join clauses)
    SELECT  *    FROM    tab1, tab2, tab3, tab4    WHERE   tab1.col = tab2.col AND        tab1.col = tab3.col AND        tab1.col = tab4.col
    Tables 1, 2, 3, and 4 are joined as:    {1 2},{1 3},{1 4}    {1 2 3},{1 3 4},{1 2 4}    {1 2 3 4}

Both examples seem to ignore the transitivity imposed by the join clauses, which creates a gap between the documentation here and what the actual optimizer does. 

For the first example, in the actual optimizer, {1,3},{1,4},{2,4} are also considered. For the second example, {2,3}, {2,4}, {3,4} are also considered. 

The reason is that, for example 1, tab1.col = tab2.col AND tab2.col = tab3.col imply that tab1.col = tab3.col due to transitivity, which leads to the consideration of {1,3}. 

The rest of the missing entries follow the same reasoning.