+WIP UP TO HERE
+
+Addition Merge Ends: If $\py \isdep \pcn$, we have already
+done the execution phase for $\pcn$ and $\py$. By
+Perfect Contents for $\pcn$, $\tipfa \pcn \haspatch \p$ i.e.
+$R \haspatch \p$. So we only need to worry about $Y = R = \tipfa \pcn$.
+By Tip Dependencies $\tipfa \pcn \ge \tipfa \py$.
+And by Tip Sources $\tipfa \py \ge $
+
+
+computed $\tipfa \py$, and by Perfect Contents for $\py$
+