strategy: split into more files

[topbloke-formulae.git] / trav-alg.tex

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+\section{Traversal phase --- algorithm}
+
+(In general, unless stated otherwise below, when we generate a new
+commit $C$ using one of the commit kind algorith, we update
+$W \assign C$.  In any such case where we say we're going to Merge
+with $L = W$, if $R \ge W$ we do not Merge but instead simply set
+$W \assign R$.)
+
+
+For each patch $\pc \in \allpatches$ in topological order by $\hasdep$,
+lowest first:
+
+\begin{enumerate}
+
+\item Optionally, attempt
+ $\alg{Merge-Base}(\pc)$.  This may or may not succeed.
+
+\item If this didn't succeed, or was not attempted, execute
+ $\alg{Recreate-Base}(\pc)$.
+
+\item Then in any case, execute
+ $\alg{Merge-Tip}(\pc)$.
+
+\end{enumerate}
+
+After processing each $\pc$ we will have created:
+
+\begin{itemize}
+
+\item $\tipcn$ and $\tipcy$ such that $\baseof{\tipcy} = \tipcn$.
+
+\end{itemize}
+
+\subsection{$\alg{Merge-Base}(\pc)$}
+
+This algorithm attempts to construct a suitably updated version of the
+base branch $\pcn$ using some existing version of $\pcn$ as a starting
+point.
+
+It should be executed noninteractively.  Specifically, if any step
+fails with a merge conflict, the whole thing should be abandoned.
+This avoids asking the user to resolve confusing conflicts.  It also
+avoids asking the user to pointlessly resolve conflicts in situations
+where we will later discover that $\alg{Merge-Base}$ wasn't feasible
+after all.
+
+If $\pc$ has only one direct dependency, this algorithm should not be
+used as in that case $\alg{Recreate-Base}$ is trivial and guaranteed
+to generate a perfect answer, whereas this algorithm might involve
+merges and therefore might not produce a perfect answer if the
+situation is complicated.
+
+Initially, set $W \iassign W^{\pcn}$.
+
+\subsubsection{Bases and sources}
+
+In some order, perhaps interleaving the two kinds of merge:
+
+\begin{enumerate}
+
+\item For each $\pd \isdirdep \pc$, find a merge base
+$M \le W,\; \le \tipdy$ and merge $\tipdy$ into $W$.
+That is, use $\alg{Merge}$ with $L = W,\; R = \tipdy$.
+(Dependency Merge.)
+
+\item For each $S \in S^{\pcn}_i$, merge it into $W$.
+That is, use $\alg{Merge}$ with $L = W,\; R = S,\; M = M^{\pcn}_i$.
+(Base Sibling Merge.)
+
+\end{enumerate}
+
+\subsubsection{Fixup}
+
+Execute $\alg{Fixup-Base}(W,\pc)$.
+
+
+\subsection{$\alg{Recreate-Base}(\pc)$}
+
+\begin{enumerate}
+
+\item
+
+Choose a $\hasdep$-maximal direct dependency $\pd$ of $\pc$.
+
+\item
+
+Use $\alg{Create Base}$ with $L$ = $\pdy,\; \pq = \pc$ to generate $C$
+and set $W \iassign C$.  (Recreate Base Beginning.)
+
+\item
+
+Execute the subalgorithm $\alg{Recreate-Recurse}(\pc)$.
+
+\item
+
+Declare that we contain all of the relevant information from the
+sources.  That is, use $\alg{Pseudo-merge}$ with $L = W, \;
+\set R = \{ W \} \cup \set S^{\pcn}$.
+(Recreate Base Final Declaration.)
+
+\end{enumerate}
+
+\subsubsection{$\alg{Recreate-Recurse}(\pd)$}
+
+\begin{enumerate}
+
+\item Is $W \haspatch \pd$ ?  If so, there is nothing to do: return.
+
+\item TODO what about non-Topbloke base branches
+
+\item Use $\alg{Pseudo-Merge}$ with $L = W,\; \set R = \{ \tipdn \}$.
+(Recreate Base Dependency Base Declaration.)
+
+\item For all $\hasdep$-maximal $\pd' \isdirdep \pd$,
+execute $\alg{Recreate-Recurse}(\pd')$.
+
+\item Use $\alg{Merge}$ to apply $\pd$ to $W$.  That is,
+$L = W, \; R = \tipdy, \; M = \baseof{R} = \tipdn$.
+(Recreate Reapply.)
+
+\end{enumerate}
+
+
+\subsection{$\alg{Merge-Tip}(\pc)$}
+
+\begin{enumerate}
+
+\item TODO CHOOSE/REFINE W AND S as was done during Ranking for bases
+
+\item $\alg{Merge}$ from $\tipcn$.  That is, $L = W, \;
+R = \tipcn$ and choose any suitable $M$.  (Tip Base Merge.)
+
+\item For each source $S \in \set S^{\pcy}$,
+$\alg{Merge}$ with $L = W, \; R = S$ and any suitable $M$.
+(Tip Source Merge.)
+
+\end{enumerate}
+
+