-When we are trying to do a merge of some kind, in general,
-we want to merge some source commits $S_0 \ldots S_n$.
-We'll write $S_0 = L$. We require that $L$ is the current git ref
-for $\patchof{L}$.
-
-\stdsection{Notation}
+Here we describe the update algorithm. This is responsible for
+refreshing patches against updated versions of their dependencies,
+for merging different versions of the various braches created by
+distributed development, and for implementing decisions to add and
+remove dependencies from patches.
+
+Broadly speaking the update proceeds as follows: during the Ranking
+phase we construct the intended graph of dependencies between patches
+(and incidentally select a merge order for the base branch of each
+patch). Then during the Traversal phase we walk that graph from the
+bottom up, constructing for each patch by a series of merges and other
+operations first a new base branch head commit and then a new tip
+branch head commit. These new head commits are maximums - that is,
+each has as ancestors all of its branches' sources and indeed all
+relevant commits in that branch.
+
+We have two possible strategies for constructing new base branch
+heads: we can either Merge (works incrementally even if there the
+patch has multiple dependencies, but may sometimes not be possible) or
+we can Regenerate (trivial if there is a single dependency, and is
+always possible, but may involve the user re-resolving conflicts if
+there are multiple dependencies).
+
+\section{Notation}
\begin{basedescript}{
\desclabelwidth{5em}
requested in the commit $K$ ($K \in \pn$) for the patch $\p$.
\item[ $\pc \hasdirdep \p$ ]
-The Topbloke commit set $\pc$ has as a direct contributors the
-commit set $\p$. This is an acyclic relation.
+The patch $\pc$ has as a direct dependency the
+patch $\p$. This is an acyclic relation.
\item[ $\p \hasdep \pq$ ]
-The commit set $\p$ has as direct or indirect contributor the commit
-set $\pq$.
+The patch $\p$ has as direct or indirect dependency the
+patch $\pq$.
Acyclic; the completion of $\hasdirdep$ into a
partial order.
-\item[ $\set E_{\pc}$ ]
-$ \bigcup_i \pendsof{S_i}{\pc} $.
-All the ends of $\pc$ in the sources.
-
-\item[ $ \grefzc, \grefcc, \grefuc, \greffc $ ]
-The git ref for the Topbloke commit set $\pc$: respectively,
-the original, current, updated, and final values.
-
-\end{basedescript}
-
-\section{Planning phase}
-
-The planning phase computes:
-\begin{itemize*}
-\item{ The relation $\hasdirdep$ and hence the ordering $\hasdep$. }
-\item{ For each commit set $\pc$, the order in which to merge
- $E_{\pc,j} \in \set E_{\pc}$. }
-\item{ For each $E_{\pc,j}$ an intended merge base $M_{\pc,j}$. }
-\end{itemize*}
-
-We use a recursive planning algorith, recursing over Topbloke commit
-sets (ie, sets $\py$ or $\pn$). We'll call the commit set we're
-processing at each step $\pc$.
-At each recursive step
-we make a plan to merge all $\set E_{\pc} = \{ E_{\pc,j \ldots} \}$
-and all the direct contributors of $\pc$ (as determined below)
-into $\grefzc$, to make $\greffc$.
-
-We start with $\pc = \pl$ where $\pl = \patchof{L}$.
-
-
-\subsection{Direct contributors for $\pc = \pcn$}
-
-The direct contributors of $\pcn$ are the commit sets corresponding to
-the tip branches for the direct dependencies of the patch $\pc$. We
-need to calculate what the direct dependencies are going to be.
-
-Choose an (arbitrary, but ideally somehow optimal in
-a way not discussed here) ordering of $\set E_{\pc}$, $E_{\pc,j}$
-($j = 1 \ldots m$).
-For brevity we will write $E_j$ for $E_{\pc,j}$.
-Remove from that set (and ordering) any $E_j$ which
-are $\le$ and $\neq$ some other $E_k$.
-
-Initially let $\set D_0 = \depsreqof{\grefzc}$.
-For each $E_j$ starting with $j=1$ choose a corresponding intended
-merge base $M_j$ such that $M_j \le E_j \land M_j \le T_{\pc,j-1}$.
-Calculate $\set D_j$ as the 3-way merge of the sets $\set D_{j-1}$ and
-$\depsreqof{E_j}$ using as a base $\depsreqof{M_j}$. This will
-generate $D_m$ as the putative direct contributors of $\pcn$.
-
-However, the invocation may give instructions that certain direct
-dependencies are definitely to be included, or excluded. As a result
-the set of actual direct contributors is some arbitrary set of patches
-(strictly, some arbitrary set of Topbloke tip commit sets).
-
-\subsection{Direct contributors for $\pc = \pcy$}
+\item[ $\pendsof{\set J}{\p}$ ]
+Convenience notation for
+the $\le$-maximal elements of $\bigcup_{J \in \set J} \pendsof{J}{\p}$
+(where $\set J$ is some set of commits).
-The sole direct contributor of $\pcy$ is $\pcn$.
+\item[ $\pendsof{\set X}{\p} \le T$ ]
+Convenience notation for
+$\bigforall_{E \in \pendsof{\set X}{\p}} E \le T$
-\subsection{Recursive step}
-
-For each direct contributor $\p$, we add the edge $\pc \hasdirdep \p$
-and augment the ordering $\hasdep$ accordingly.
-
-If this would make a cycle in $\hasdep$, we abort . The operation must
-then be retried by the user, if desired, but with different or
-additional instructions for modifying the direct contributors of some
-$\pqn$ involved in the cycle.
-
-For each such $\p$, after updating $\hasdep$, we recursively make a plan
-for $\pc' = \p$.
-
-\section{Execution phase}
+\item[ $\allsrcs$ ]
+$\bigcup_{\p \in \allpatches} \set H^{\pn} \cup \set H^{\py}$.
+All the input commits to the update algorithm. (See below.)
+%\item[ $\set E_{\pc}$ ]
+%$ \bigcup_i \pendsof{S_{\pc,i}}{\pc} $.
+%All the ends of $\pc$ in the sources.
+%\item[ $ \tipzc, \tipcc, \tipuc, \tipfc $ ]
+%The git ref for the Topbloke commit set $\pc$: respectively,
+%the original, current, updated, and final values.
+\end{basedescript}
-with $M=M_j, L=T_{\pc,j-1}, R=E_j$,
-and calculate what the resulting desired direct dependencies file
-(ie, the set of patches $\set D_j$)
-would be. Eventually we
+\stdsection{Inputs to the update algorithm}
-So, formally, we select somehow an order of sources $S_i$. For each
+\begin{basedescript}{
+\desclabelwidth{5em}
+\desclabelstyle{\nextlinelabel}
+}
+\item[ $\pc_0$ ]
+The topmost patch which we are trying to update. This and
+all of its dependencies will be updated.
+
+\item[ $h : \pc^{+/-} \mapsto \set H^{\pc^{+/-}}$ ]
+Function for getting the existing heads $\set H$ of the branch $\pc^{+/-}$.
+These are the heads which will be merged and used in this update.
+This will include the current local and remote git refs, as desired.
+
+\item[ $g : \pc, \Gamma \mapsto \Gamma'$ ]
+Function to allow explicit adjustment of the direct dependencies
+of $\pc$. It is provided with a putative set of direct dependencies
+$\Gamma$ computed as an appropriate merge of the dependencies requested by the
+sources and should return the complete actual set $\Gamma'$ of direct
+dependencies to use. This allows the specification of any desired
+(acyclic) relations $\hasdirdep$ and $\hasdep$.
+\end{basedescript}
-Make use of the following recursive algorithm, Plan
+\stdsection{Important variables and values in the update algorithm}
+\begin{basedescript}{
+\desclabelwidth{5em}
+\desclabelstyle{\nextlinelabel}
+}
+\item[ $\Gamma_{\pc}$ ]
+The desired direct dependencies of $\pc$, a set of patches.
+\item[ $\allpatches$ ]
+The set of all the patches we are dealing with (constructed
+during the update algorithm).
+\item[ $\tipcn, \tipcy$ ]
+The new tips of the git branches $\pcn$ and $\pcy$, containing
+all the correct commits (and the correct other patches), as
+generated by the Traversal phase of the update algorithm.
- recursively make a plan to merge all $E = \pends$
+\end{basedescript}
-Specifically, in
~ian / topbloke-formulae.git / blobdiff