1 \section{Traversal phase --- algorithm}
3 (In general, unless stated otherwise below, when we generate a new
4 commit $C$ using one of the commit kind recipies, we update
5 $W \assign C$. In any such case where we say we're going to Merge
6 with $L = W$, if $R \ge W$ we do not Merge but instead simply set
10 For each patch $\pc \in \allpatches$ in topological order by $\hasdep$,
15 \item Optionally, attempt
16 $\alg{Merge-Base}(\pc)$. This may or may not succeed.
18 \item If this didn't succeed, or was not attempted, execute
19 $\alg{Recreate-Base}(\pc)$.
21 \item Then in any case, execute
22 $\alg{Merge-Tip}(\pc)$.
26 After processing each $\pc$ we will have created $\tipcn$ and $\tipcy$
29 \statement{Correct Base}{
30 \baseof{\tipcy} = \tipcn
32 \statement{Tip Exceeds Inputs}{
33 \tipcy \ge \pendsof{\allsrcs}{\pcy}
35 \statement{Base Exceeds Inputs' Bases}{
36 \bigforall_{E \in \pendsof{\allsrcs}{\pcy}} \tipcn \ge \baseof{E}
38 \statement{Base Exceeds Base Inputs}{
39 \bigforall_{H \in \set H^{\pn}} \tipcn \ge H
42 \subsection{$\alg{Merge-Base}(\pc)$}
44 This algorithm attempts to construct a suitably updated version of the
45 base branch $\pcn$ using some existing version of $\pcn$ as a starting
48 It should be executed noninteractively. Specifically, if any step
49 fails with a merge conflict, the whole thing should be abandoned.
50 This avoids asking the user to resolve confusing conflicts. It also
51 avoids asking the user to pointlessly resolve conflicts in situations
52 where we will later discover that $\alg{Merge-Base}$ wasn't feasible
55 If $\pc$ has only one direct dependency, this algorithm should not be
56 used as in that case $\alg{Recreate-Base}$ is trivial and guaranteed
57 to generate a perfect answer, whereas this algorithm might involve
58 merges and therefore might not produce a perfect answer if the
59 situation is complicated.
61 Initially, set $W \iassign W^{\pcn}$.
63 \subsubsection{Bases and sources}
65 In some order, perhaps interleaving the two kinds of merge:
69 \item For each $\pd \isdirdep \pc$, find a merge base
70 $M \le W,\; \le \tipdy$ and merge $\tipdy$ into $W$.
71 That is, use $\alg{Merge}$ with $L = W,\; R = \tipdy$.
74 \item For each $S \in S^{\pcn}_i$, merge it into $W$.
75 That is, use $\alg{Merge}$ with $L = W,\; R = S,\; M = M^{\pcn}_i$.
82 Execute $\alg{Fixup-Base}(W,\pc)$.
85 \subsection{$\alg{Recreate-Base}(\pc)$}
91 Choose a $\hasdep$-maximal direct dependency $\pd$ of $\pc$.
95 Use $\alg{Create Base}$ with $L$ = $\pdy,\; \pq = \pc$ to generate $C$
96 and set $W \iassign C$. (Recreate Base Beginning.)
100 Execute the subalgorithm $\alg{Recreate-Recurse}(\pc)$.
104 Declare that we contain all of the relevant information from the
105 sources. That is, use $\alg{Pseudo-Merge}$ with $L = W, \;
106 \set R = \{ W \} \cup \set S^{\pcn}$.
107 (Recreate Base Final Declaration.)
111 \subsubsection{$\alg{Recreate-Recurse}(\pd)$}
115 \item Is $W \haspatch \pd$ ? If so, there is nothing to do: return.
117 \item TODO what about non-Topbloke base branches
119 \item For all $\hasdep$-maximal $\pd' \isdirdep \pd$,
120 execute $\alg{Recreate-Recurse}(\pd')$.
122 \item Use $\alg{Pseudo-Merge}$ with $L = W,\; \set R = \{ \tipdn \}$.
123 (Recreate Base Dependency Base Declaration.)
125 \item Use $\alg{Merge}$ to apply $\pd$ to $W$. That is,
126 $L = W, \; R = \tipdy, \; M = \baseof{R} = \tipdn$.
132 \subsection{$\alg{Merge-Tip}(\pc)$}
136 \item TODO CHOOSE/REFINE W AND S as was done during Ranking for bases
138 \item $\alg{Merge}$ from $\tipcn$. That is, $L = W, \;
139 R = \tipcn$ and choose any suitable $M$. (Tip Base Merge.)
141 \item For each source $S \in \set S^{\pcy}$,
142 $\alg{Merge}$ with $L = W, \; R = S$ and any suitable $M$.