merge any Topbloke-controlled branch into any plain git branch.
Given those conditions, Tip Merge and Merge Acyclic do not apply.
-And by Foreign Contents for Y, $\forall_{\p, D \in \py} D \not\le Y$
+And by Foreign Contents for (wlog) Y, $\forall_{\p, D \in \py} D \not\le Y$
so then by No Replay $D \not\isin Y$
so $\neg [ Y \haspatch \p ]$ so neither
Merge Ends condition applies.
putative ancestor $A \in \pn$ and see whether $A \le C$.
By Exact Ancestors for C, $A \le C \equiv A \le L \lor A \le R \lor A = C$.
-But $C \in py$ and $A \in \pn$ so $A \neq C$.
+But $C \in \py$ and $A \in \pn$ so $A \neq C$.
Thus $A \le C \equiv A \le L \lor A \le R$.
By Unique Base of L and Transitive Ancestors,