1 \documentclass[a4paper,leqno]{strayman}
3 \let\numberwithin=\notdef
11 \renewcommand{\ge}{\geqslant}
12 \renewcommand{\le}{\leqslant}
13 \newcommand{\nge}{\ngeqslant}
14 \newcommand{\nle}{\nleqslant}
16 \newcommand{\has}{\sqsupseteq}
17 \newcommand{\isin}{\sqsubseteq}
19 \newcommand{\nothaspatch}{\mathrel{\,\not\!\not\relax\haspatch}}
20 \newcommand{\notpatchisin}{\mathrel{\,\not\!\not\relax\patchisin}}
21 \newcommand{\haspatch}{\sqSupset}
22 \newcommand{\patchisin}{\sqSubset}
24 \newif\ifhidehack\hidehackfalse
25 \DeclareRobustCommand\hidefromedef[2]{%
26 \hidehacktrue\ifhidehack#1\else#2\fi\hidehackfalse}
27 \newcommand{\pa}[1]{\hidefromedef{\varmathbb{#1}}{#1}}
29 \newcommand{\set}[1]{\mathbb{#1}}
30 \newcommand{\pay}[1]{\pa{#1}^+}
31 \newcommand{\pan}[1]{\pa{#1}^-}
33 \newcommand{\p}{\pa{P}}
34 \newcommand{\py}{\pay{P}}
35 \newcommand{\pn}{\pan{P}}
37 \newcommand{\pr}{\pa{R}}
38 \newcommand{\pry}{\pay{R}}
39 \newcommand{\prn}{\pan{R}}
41 %\newcommand{\hasparents}{\underaccent{1}{>}}
42 %\newcommand{\hasparents}{{%
43 % \declareslashed{}{_{_1}}{0}{-0.8}{>}\slashed{>}}}
44 \newcommand{\hasparents}{>_{\mkern-7.0mu _1}}
45 \newcommand{\areparents}{<_{\mkern-14.0mu _1\mkern+5.0mu}}
47 \renewcommand{\implies}{\Rightarrow}
48 \renewcommand{\equiv}{\Leftrightarrow}
49 \renewcommand{\nequiv}{\nLeftrightarrow}
50 \renewcommand{\land}{\wedge}
51 \renewcommand{\lor}{\vee}
53 \newcommand{\pancs}{{\mathcal A}}
54 \newcommand{\pends}{{\mathcal E}}
56 \newcommand{\pancsof}[2]{\pancs ( #1 , #2 ) }
57 \newcommand{\pendsof}[2]{\pends ( #1 , #2 ) }
59 \newcommand{\merge}{{\mathcal M}}
60 \newcommand{\mergeof}[4]{\merge(#1,#2,#3,#4)}
61 %\newcommand{\merge}[4]{{#2 {{\frac{ #1 }{ #3 } #4}}}}
63 \newcommand{\patch}{{\mathcal P}}
64 \newcommand{\base}{{\mathcal B}}
66 \newcommand{\patchof}[1]{\patch ( #1 ) }
67 \newcommand{\baseof}[1]{\base ( #1 ) }
69 \newcommand{\eqntag}[2]{ #2 \tag*{\mbox{#1}} }
70 \newcommand{\eqn}[2]{ #2 \tag*{\mbox{\bf #1}} }
72 %\newcommand{\bigforall}{\mathop{\hbox{\huge$\forall$}}}
73 \newcommand{\bigforall}{%
75 {\hbox{\huge$\forall$}}%
76 {\hbox{\Large$\forall$}}%
77 {\hbox{\normalsize$\forall$}}%
78 {\hbox{\scriptsize$\forall$}}}%
81 \newcommand{\Largeexists}{\mathop{\hbox{\Large$\exists$}}}
82 \newcommand{\Largenexists}{\mathop{\hbox{\Large$\nexists$}}}
84 \newcommand{\qed}{\square}
85 \newcommand{\proofstarts}{{\it Proof:}}
86 \newcommand{\proof}[1]{\proofstarts #1 $\qed$}
88 \newcommand{\gathbegin}{\begin{gather} \tag*{}}
89 \newcommand{\gathnext}{\\ \tag*{}}
92 \newcommand{\false}{f}
100 \desclabelstyle{\nextlinelabel}
102 \item[ $ C \hasparents \set X $ ]
103 The parents of commit $C$ are exactly the set
107 $C$ is a descendant of $D$ in the git commit
108 graph. This is a partial order, namely the transitive closure of
109 $ D \in \set X $ where $ C \hasparents \set X $.
111 \item[ $ C \has D $ ]
112 Informally, the tree at commit $C$ contains the change
113 made in commit $D$. Does not take account of deliberate reversions by
114 the user or reversion, rebasing or rewinding in
115 non-Topbloke-controlled branches. For merges and Topbloke-generated
116 anticommits or re-commits, the ``change made'' is only to be thought
117 of as any conflict resolution. This is not a partial order because it
120 \item[ $ \p, \py, \pn $ ]
121 A patch $\p$ consists of two sets of commits $\pn$ and $\py$, which
122 are respectively the base and tip git branches. $\p$ may be used
123 where the context requires a set, in which case the statement
124 is to be taken as applying to both $\py$ and $\pn$.
125 None of these sets overlap. Hence:
127 \item[ $ \patchof{ C } $ ]
128 Either $\p$ s.t. $ C \in \p $, or $\bot$.
129 A function from commits to patches' sets $\p$.
131 \item[ $ \pancsof{C}{\set P} $ ]
132 $ \{ A \; | \; A \le C \land A \in \set P \} $
133 i.e. all the ancestors of $C$
134 which are in $\set P$.
136 \item[ $ \pendsof{C}{\set P} $ ]
137 $ \{ E \; | \; E \in \pancsof{C}{\set P}
138 \land \mathop{\not\exists}_{A \in \pancsof{C}{\set P}}
139 E \neq A \land E \le A \} $
140 i.e. all $\le$-maximal commits in $\pancsof{C}{\set P}$.
142 \item[ $ \baseof{C} $ ]
143 $ \pendsof{C}{\pn} = \{ \baseof{C} \} $ where $ C \in \py $.
144 A partial function from commits to commits.
145 See Unique Base, below.
147 \item[ $ C \haspatch \p $ ]
148 $\displaystyle \bigforall_{D \in \py} D \isin C \equiv D \le C $.
149 ~ Informally, $C$ has the contents of $\p$.
151 \item[ $ C \nothaspatch \p $ ]
152 $\displaystyle \bigforall_{D \in \py} D \not\isin C $.
153 ~ Informally, $C$ has none of the contents of $\p$.
155 Non-Topbloke commits are $\nothaspatch \p$ for all $\p$. This
156 includes commits on plain git branches made by applying a Topbloke
158 patch is applied to a non-Topbloke branch and then bubbles back to
159 the relevant Topbloke branches, we hope that
160 if the user still cares about the Topbloke patch,
161 git's merge algorithm will DTRT when trying to re-apply the changes.
163 \item[ $\displaystyle \mergeof{C}{L}{M}{R} $ ]
164 The contents of a git merge result:
166 $\displaystyle D \isin C \equiv
168 (D \isin L \land D \isin R) \lor D = C : & \true \\
169 (D \not\isin L \land D \not\isin R) \land D \neq C : & \false \\
170 \text{otherwise} : & D \not\isin M
178 We maintain these each time we construct a new commit. \\
180 C \has D \implies C \ge D
182 \[\eqn{Unique Base:}{
183 \bigforall_{C \in \py} \pendsof{C}{\pn} = \{ B \}
185 \[\eqn{Tip Contents:}{
186 \bigforall_{C \in \py} D \isin C \equiv
187 { D \isin \baseof{C} \lor \atop
188 (D \in \py \land D \le C) }
190 \[\eqn{Base Acyclic:}{
191 \bigforall_{B \in \pn} D \isin B \implies D \notin \py
194 \bigforall_{C,\p} C \haspatch \p \lor C \nothaspatch \p
196 \[\eqn{Foreign Inclusion:}{
197 \bigforall_{D \text{ s.t. } \patchof{D} = \bot} D \isin C \equiv D \leq C
200 \section{Some lemmas}
202 \[ \eqn{Alternative (overlapping) formulations defining
203 $\mergeof{C}{L}{M}{R}$:}{
206 D \isin L \equiv D \isin R : & D = C \lor D \isin L \\
207 D \isin L \nequiv D \isin R : & D = C \lor D \not\isin M \\
208 D \isin L \equiv D \isin M : & D = C \lor D \isin R \\
209 D \isin L \nequiv D \isin M : & D = C \lor D \isin L \\
210 \text{as above with L and R exchanged}
216 Original definition is symmetrical in $L$ and $R$.
219 \[ \eqn{Exclusive Tip Contents:}{
220 \bigforall_{C \in \py}
221 \neg \Bigl[ D \isin \baseof{C} \land ( D \in \py \land D \le C )
224 Ie, the two limbs of the RHS of Tip Contents are mutually exclusive.
227 Let $B = \baseof{C}$ in $D \isin \baseof{C}$. Now $B \in \pn$.
228 So by Base Acyclic $D \isin B \implies D \notin \py$.
230 \[ \eqntag{{\it Corollary - equivalent to Tip Contents}}{
231 \bigforall_{C \in \py} D \isin C \equiv
233 D \in \py : & D \le C \\
234 D \not\in \py : & D \isin \baseof{C}
238 \[ \eqn{Tip Self Inpatch:}{
239 \bigforall_{C \in \py} C \haspatch \p
241 Ie, tip commits contain their own patch.
244 Apply Exclusive Tip Contents to some $D \in \py$:
245 $ \bigforall_{C \in \py}\bigforall_{D \in \py}
246 D \isin C \equiv D \le C $
249 \[ \eqn{Exact Ancestors:}{
250 \bigforall_{ C \hasparents \set{R} }
252 ( \mathop{\hbox{\huge{$\vee$}}}_{R \in \set R} D \le R )
257 \[ \eqn{Transitive Ancestors:}{
258 \left[ \bigforall_{ E \in \pendsof{C}{\set P} } E \le M \right] \equiv
259 \left[ \bigforall_{ A \in \pancsof{C}{\set P} } A \le M \right]
263 The implication from right to left is trivial because
264 $ \pends() \subset \pancs() $.
265 For the implication from left to right:
266 by the definition of $\mathcal E$,
267 for every such $A$, either $A \in \pends()$ which implies
268 $A \le M$ by the LHS directly,
269 or $\exists_{A' \in \pancs()} \; A' \neq A \land A \le A' $
270 in which case we repeat for $A'$. Since there are finitely many
271 commits, this terminates with $A'' \in \pends()$, ie $A'' \le M$
272 by the LHS. And $A \le A''$.
275 \[ \eqn{Calculation Of Ends:}{
276 \bigforall_{C \hasparents \set A}
277 \pendsof{C}{\set P} =
281 C \not\in \p : & \displaystyle
283 \Bigl[ \Largeexists_{A \in \set A}
284 E \in \pendsof{A}{\set P} \Bigr] \land
285 \Bigl[ \Largenexists_{B \in \set A}
286 E \neq B \land E \le B \Bigr]
292 \subsection{No Replay for Merge Results}
294 If we are constructing $C$, with,
302 No Replay is preserved. \proofstarts
304 \subsubsection{For $D=C$:} $D \isin C, D \le C$. OK.
306 \subsubsection{For $D \isin L \land D \isin R$:}
307 $D \isin C$. And $D \isin L \implies D \le L \implies D \le C$. OK.
309 \subsubsection{For $D \neq C \land D \not\isin L \land D \not\isin R$:}
312 \subsubsection{For $D \neq C \land (D \isin L \equiv D \not\isin R)
313 \land D \not\isin M$:}
314 $D \isin C$. Also $D \isin L \lor D \isin R$ so $D \le L \lor D \le
317 \subsubsection{For $D \neq C \land (D \isin L \equiv D \not\isin R)
323 \section{Commit annotation}
325 We annotate each Topbloke commit $C$ with:
329 \baseof{C}, \text{ if } C \in \py
332 \text{ either } C \haspatch \pa{Q} \text{ or } C \nothaspatch \pa{Q}
334 \bigforall_{\pay{Q} \not\ni C} \pendsof{C}{\pay{Q}}
337 $\patchof{C}$, for each kind of Topbloke-generated commit, is stated
338 in the summary in the section for that kind of commit.
340 Whether $\baseof{C}$ is required, and if so what the value is, is
341 stated in the proof of Unique Base for each kind of commit.
343 $C \haspatch \pa{Q}$ or $\nothaspatch \pa{Q}$ is represented as the
344 set $\{ \pa{Q} | C \haspatch \pa{Q} \}$. Whether $C \haspatch \pa{Q}$
346 (in terms of $I \haspatch \pa{Q}$ or $I \nothaspatch \pa{Q}$
347 for the ingredients $I$),
348 in the proof of Coherence for each kind of commit.
350 $\pendsof{C}{\pa{Q}^+}$ is computed, for all Topbloke-generated commits,
351 using the lemma Calculation of Ends, above.
352 We do not annotate $\pendsof{C}{\py}$ for $C \in \py$. Doing so would
353 make it wrong to make plain commits with git because the recorded $\pends$
354 would have to be updated. The annotation is not needed in that case
355 because $\forall_{\py \ni C} \; \pendsof{C}{\py} = \{C\}$.
357 \section{Simple commit}
359 A simple single-parent forward commit $C$ as made by git-commit.
361 \tag*{} C \hasparents \{ A \} \\
362 \tag*{} \patchof{C} = \patchof{A} \\
363 \tag*{} D \isin C \equiv D \isin A \lor D = C
365 This also covers Topbloke-generated commits on plain git branches:
366 Topbloke strips the metadata when exporting.
368 \subsection{No Replay}
371 \subsection{Unique Base}
372 If $A, C \in \py$ then by Calculation of Ends for
373 $C, \py, C \not\in \py$:
374 $\pendsof{C}{\pn} = \pendsof{A}{\pn}$ so
375 $\baseof{C} = \baseof{A}$. $\qed$
377 \subsection{Tip Contents}
378 We need to consider only $A, C \in \py$. From Tip Contents for $A$:
379 \[ D \isin A \equiv D \isin \baseof{A} \lor ( D \in \py \land D \le A ) \]
380 Substitute into the contents of $C$:
381 \[ D \isin C \equiv D \isin \baseof{A} \lor ( D \in \py \land D \le A )
383 Since $D = C \implies D \in \py$,
384 and substituting in $\baseof{C}$, this gives:
385 \[ D \isin C \equiv D \isin \baseof{C} \lor
386 (D \in \py \land D \le A) \lor
387 (D = C \land D \in \py) \]
388 \[ \equiv D \isin \baseof{C} \lor
389 [ D \in \py \land ( D \le A \lor D = C ) ] \]
390 So by Exact Ancestors:
391 \[ D \isin C \equiv D \isin \baseof{C} \lor ( D \in \py \land D \le C
395 \subsection{Base Acyclic}
397 Need to consider only $A, C \in \pn$.
399 For $D = C$: $D \in \pn$ so $D \not\in \py$. OK.
401 For $D \neq C$: $D \isin C \equiv D \isin A$, so by Base Acyclic for
402 $A$, $D \isin C \implies D \not\in \py$.
406 \subsection{Coherence and patch inclusion}
408 Need to consider $D \in \py$
410 \subsubsection{For $A \haspatch P, D = C$:}
416 $ D \isin C \equiv \ldots \lor \true \text{ so } D \haspatch C $.
418 \subsubsection{For $A \haspatch P, D \neq C$:}
419 Ancestors: $ D \le C \equiv D \le A $.
421 Contents: $ D \isin C \equiv D \isin A \lor f $
422 so $ D \isin C \equiv D \isin A $.
425 \[ A \haspatch P \implies C \haspatch P \]
427 \subsubsection{For $A \nothaspatch P$:}
429 Firstly, $C \not\in \py$ since if it were, $A \in \py$.
432 Now by contents of $A$, $D \notin A$, so $D \notin C$.
435 \[ A \nothaspatch P \implies C \nothaspatch P \]
438 \subsection{Foreign inclusion:}
440 If $D = C$, trivial. For $D \neq C$:
441 $D \isin C \equiv D \isin A \equiv D \le A \equiv D \le C$. $\qed$
443 \section{Create Base}
453 Given $L, R^+, R^-$ where
454 $R^+ \in \pry, R^- = \baseof{R^+}$.
455 Construct $C$ which has $\pr$ removed.
456 Used for removing a branch dependency.
458 C \hasparents \{ L \}
460 \patchof{C} = \patchof{L}
462 \mergeof{C}{L}{R^+}{R^-}
465 \subsection{Conditions}
467 \[ \eqn{ Into Base }{
470 \[ \eqn{ Unique Tip }{
471 \pendsof{L}{\pry} = \{ R^+ \}
473 \[ \eqn{ Currently Included }{
477 \subsection{Ordering of ${L, R^+, R^-}$:}
479 By Unique Tip, $R^+ \le L$. By definition of $\base$, $R^- \le R^+$
480 so $R^- \le L$. So $R^+ \le C$ and $R^- \le C$.
483 (Note that the merge base $R^+ \not\le R^-$, i.e. the merge base is
484 later than one of the branches to be merged.)
486 \subsection{No Replay}
488 No Replay for Merge Results applies. $\qed$
490 \subsection{Desired Contents}
492 \[ D \isin C \equiv [ D \notin \pry \land D \isin L ] \lor D = C \]
495 \subsubsection{For $D = C$:}
497 Trivially $D \isin C$. OK.
499 \subsubsection{For $D \neq C, D \not\le L$:}
501 By No Replay $D \not\isin L$. Also $D \not\le R^-$ hence
502 $D \not\isin R^-$. Thus $D \not\isin C$. OK.
504 \subsubsection{For $D \neq C, D \le L, D \in \pry$:}
506 By Currently Included, $D \isin L$.
508 By Tip Self Inpatch, $D \isin R^+ \equiv D \le R^+$, but by
509 by Unique Tip, $D \le R^+ \equiv D \le L$.
512 By Base Acyclic, $D \not\isin R^-$.
514 Apply $\merge$: $D \not\isin C$. OK.
516 \subsubsection{For $D \neq C, D \le L, D \notin \pry$:}
518 By Tip Contents for $R^+$, $D \isin R^+ \equiv D \isin R^-$.
520 Apply $\merge$: $D \isin C \equiv D \isin L$. OK.
524 \subsection{Unique Base}
526 Into Base means that $C \in \pn$, so Unique Base is not
529 \subsection{Tip Contents}
531 Again, not applicable. $\qed$
533 \subsection{Base Acyclic}
535 By Base Acyclic for $L$, $D \isin L \implies D \not\in \py$.
536 And by Into Base $C \not\in \py$.
537 Now from Desired Contents, above, $D \isin C
538 \implies D \isin L \lor D = C$, which thus
539 $\implies D \not\in \py$. $\qed$.
541 \subsection{Coherence and Patch Inclusion}
543 Need to consider some $D \in \py$. By Into Base, $D \neq C$.
545 \subsubsection{For $\p = \pr$:}
546 By Desired Contents, above, $D \not\isin C$.
547 So $C \nothaspatch \pr$.
549 \subsubsection{For $\p \neq \pr$:}
550 By Desired Contents, $D \isin C \equiv D \isin L$
551 (since $D \in \py$ so $D \not\in \pry$).
553 If $L \nothaspatch \p$, $D \not\isin L$ so $D \not\isin C$.
554 So $L \nothaspatch \p \implies C \nothaspatch \p$.
556 Whereas if $L \haspatch \p$, $D \isin L \equiv D \le L$.
557 so $L \haspatch \p \implies C \haspatch \p$.
561 \section{Foreign Inclusion}
563 Consider some $D$ s.t. $\patchof{D} = \bot$. $D \neq C$.
564 So by Desired Contents $D \isin C \equiv D \isin L$.
565 By Foreign Inclusion of $D$ in $L$, $D \isin L \equiv D \le L$.
567 And $D \le C \equiv D \le L$.
568 Thus $D \isin C \equiv D \le C$.
574 Merge commits $L$ and $R$ using merge base $M$ ($M < L, M < R$):
576 C \hasparents \{ L, R \}
578 \patchof{C} = \patchof{L}
582 We will occasionally use $X,Y$ s.t. $\{X,Y\} = \{L,R\}$.
584 \subsection{Conditions}
586 \[ \eqn{ Tip Merge }{
589 R \in \py : & \baseof{R} \ge \baseof{L}
590 \land [\baseof{L} = M \lor \baseof{L} = \baseof{M}] \\
591 R \in \pn : & M = \baseof{L} \\
592 \text{otherwise} : & \false
595 \[ \eqn{ Merge Acyclic }{
600 \[ \eqn{ Removal Merge Ends }{
601 X \not\haspatch \p \land
605 \pendsof{Y}{\py} = \pendsof{M}{\py}
607 \[ \eqn{ Addition Merge Ends }{
608 X \not\haspatch \p \land
612 \bigforall_{E \in \pendsof{X}{\py}} E \le Y
616 \subsection{Non-Topbloke merges}
618 We require both $\patchof{L} = \bot$ and $\patchof{R} = \bot$.
619 I.e. not only is it forbidden to merge into a Topbloke-controlled
620 branch without Topbloke's assistance, it is also forbidden to
621 merge any Topbloke-controlled branch into any plain git branch.
623 Given those conditions, Tip Merge and Merge Acyclic do not apply.
624 And $Y \not\in \py$ so $\neg [ Y \haspatch \p ]$ so neither
625 Merge Ends condition applies. Good.
627 \subsection{No Replay}
629 No Replay for Merge Results applies. $\qed$
631 \subsection{Unique Base}
633 Need to consider only $C \in \py$, ie $L \in \py$,
634 and calculate $\pendsof{C}{\pn}$. So we will consider some
635 putative ancestor $A \in \pn$ and see whether $A \le C$.
637 By Exact Ancestors for C, $A \le C \equiv A \le L \lor A \le R \lor A = C$.
638 But $C \in py$ and $A \in \pn$ so $A \neq C$.
639 Thus $A \le C \equiv A \le L \lor A \le R$.
641 By Unique Base of L and Transitive Ancestors,
642 $A \le L \equiv A \le \baseof{L}$.
644 \subsubsection{For $R \in \py$:}
646 By Unique Base of $R$ and Transitive Ancestors,
647 $A \le R \equiv A \le \baseof{R}$.
649 But by Tip Merge condition on $\baseof{R}$,
650 $A \le \baseof{L} \implies A \le \baseof{R}$, so
651 $A \le \baseof{R} \lor A \le \baseof{L} \equiv A \le \baseof{R}$.
652 Thus $A \le C \equiv A \le \baseof{R}$.
653 That is, $\baseof{C} = \baseof{R}$.
655 \subsubsection{For $R \in \pn$:}
657 By Tip Merge condition on $R$ and since $M \le R$,
658 $A \le \baseof{L} \implies A \le R$, so
659 $A \le R \lor A \le \baseof{L} \equiv A \le R$.
660 Thus $A \le C \equiv A \le R$.
661 That is, $\baseof{C} = R$.
665 \subsection{Coherence and Patch Inclusion}
667 Need to determine $C \haspatch \p$ based on $L,M,R \haspatch \p$.
668 This involves considering $D \in \py$.
670 \subsubsection{For $L \nothaspatch \p, R \nothaspatch \p$:}
671 $D \not\isin L \land D \not\isin R$. $C \not\in \py$ (otherwise $L
672 \in \py$ ie $L \haspatch \p$ by Tip Self Inpatch). So $D \neq C$.
673 Applying $\merge$ gives $D \not\isin C$ i.e. $C \nothaspatch \p$.
675 \subsubsection{For $L \haspatch \p, R \haspatch \p$:}
676 $D \isin L \equiv D \le L$ and $D \isin R \equiv D \le R$.
677 (Likewise $D \isin X \equiv D \le X$ and $D \isin Y \equiv D \le Y$.)
679 Consider $D = C$: $D \isin C$, $D \le C$, OK for $C \haspatch \p$.
681 For $D \neq C$: $D \le C \equiv D \le L \lor D \le R
682 \equiv D \isin L \lor D \isin R$.
683 (Likewise $D \le C \equiv D \le X \lor D \le Y$.)
685 Consider $D \neq C, D \isin X \land D \isin Y$:
686 By $\merge$, $D \isin C$. Also $D \le X$
687 so $D \le C$. OK for $C \haspatch \p$.
689 Consider $D \neq C, D \not\isin X \land D \not\isin Y$:
690 By $\merge$, $D \not\isin C$.
691 And $D \not\le X \land D \not\le Y$ so $D \not\le C$.
692 OK for $C \haspatch \p$.
694 Remaining case, wlog, is $D \not\isin X \land D \isin Y$.
695 $D \not\le X$ so $D \not\le M$ so $D \not\isin M$.
696 Thus by $\merge$, $D \isin C$. And $D \le Y$ so $D \le C$.
697 OK for $C \haspatch \p$.
699 So indeed $L \haspatch \p \land R \haspatch \p \implies C \haspatch \p$.
701 \subsubsection{For (wlog) $X \not\haspatch \p, Y \haspatch \p$:}
703 $M \haspatch \p \implies C \nothaspatch \p$.
704 $M \nothaspatch \p \implies C \haspatch \p$.
708 One of the Merge Ends conditions applies.
709 Recall that we are considering $D \in \py$.
710 $D \isin Y \equiv D \le Y$. $D \not\isin X$.
711 We will show for each of
712 various cases that $D \isin C \equiv M \nothaspatch \p \land D \le C$
713 (which suffices by definition of $\haspatch$ and $\nothaspatch$).
715 Consider $D = C$: Thus $C \in \py, L \in \py$, and by Tip
716 Self Inpatch $L \haspatch \p$, so $L=Y, R=X$. By Tip Merge,
717 $M=\baseof{L}$. So by Base Acyclic $D \not\isin M$, i.e.
718 $M \nothaspatch \p$. And indeed $D \isin C$ and $D \le C$. OK.
720 Consider $D \neq C, M \nothaspatch P, D \isin Y$:
721 $D \le Y$ so $D \le C$.
722 $D \not\isin M$ so by $\merge$, $D \isin C$. OK.
724 Consider $D \neq C, M \nothaspatch P, D \not\isin Y$:
725 $D \not\le Y$. If $D \le X$ then
726 $D \in \pancsof{X}{\py}$, so by Addition Merge Ends and
727 Transitive Ancestors $D \le Y$ --- a contradiction, so $D \not\le X$.
728 Thus $D \not\le C$. By $\merge$, $D \not\isin C$. OK.
730 Consider $D \neq C, M \haspatch P, D \isin Y$:
731 $D \le Y$ so $D \in \pancsof{Y}{\py}$ so by Removal Merge Ends
732 and Transitive Ancestors $D \in \pancsof{M}{\py}$ so $D \le M$.
733 Thus $D \isin M$. By $\merge$, $D \not\isin C$. OK.
735 Consider $D \neq C, M \haspatch P, D \not\isin Y$:
736 By $\merge$, $D \not\isin C$. OK.
740 \subsection{Base Acyclic}
742 This applies when $C \in \pn$.
743 $C \in \pn$ when $L \in \pn$ so by Merge Acyclic, $R \nothaspatch \p$.
745 Consider some $D \in \py$.
747 By Base Acyclic of $L$, $D \not\isin L$. By the above, $D \not\isin
748 R$. And $D \neq C$. So $D \not\isin C$.
752 \subsection{Tip Contents}
754 We need worry only about $C \in \py$.
755 And $\patchof{C} = \patchof{L}$
756 so $L \in \py$ so $L \haspatch \p$. We will use the Unique Base
757 of $C$, and its Coherence and Patch Inclusion, as just proved.
759 Firstly we show $C \haspatch \p$: If $R \in \py$, then $R \haspatch
760 \p$ and by Coherence/Inclusion $C \haspatch \p$ . If $R \not\in \py$
761 then by Tip Merge $M = \baseof{L}$ so by Base Acyclic and definition
762 of $\nothaspatch$, $M \nothaspatch \p$. So by Coherence/Inclusion $C
763 \haspatch \p$ (whether $R \haspatch \p$ or $\nothaspatch$).
765 We will consider an arbitrary commit $D$
766 and prove the Exclusive Tip Contents form.
768 \subsubsection{For $D \in \py$:}
769 $C \haspatch \p$ so by definition of $\haspatch$, $D \isin C \equiv D
772 \subsubsection{For $D \not\in \py, R \not\in \py$:}
774 $D \neq C$. By Tip Contents of $L$,
775 $D \isin L \equiv D \isin \baseof{L}$, and by Tip Merge condition,
776 $D \isin L \equiv D \isin M$. So by definition of $\merge$, $D \isin
777 C \equiv D \isin R$. And $R = \baseof{C}$ by Unique Base of $C$.
778 Thus $D \isin C \equiv D \isin \baseof{C}$. OK.
780 \subsubsection{For $D \not\in \py, R \in \py$:}
785 $D \isin L \equiv D \isin \baseof{L}$ and
786 $D \isin R \equiv D \isin \baseof{R}$.
788 If $\baseof{L} = M$, trivially $D \isin M \equiv D \isin \baseof{L}.$
789 Whereas if $\baseof{L} = \baseof{M}$, by definition of $\base$,
790 $\patchof{M} = \patchof{L} = \py$, so by Tip Contents of $M$,
791 $D \isin M \equiv D \isin \baseof{M} \equiv D \isin \baseof{L}$.
793 So $D \isin M \equiv D \isin L$ and by $\merge$,
794 $D \isin C \equiv D \isin R$. But from Unique Base,
795 $\baseof{C} = R$ so $D \isin C \equiv D \isin \baseof{C}$. OK.
799 \subsection{Foreign Inclusion}
801 Consider some $D$ s.t. $\patchof{D} = \bot$.
802 By Foreign Inclusion of $L, M, R$:
803 $D \isin L \equiv D \le L$;
804 $D \isin M \equiv D \le M$;
805 $D \isin R \equiv D \le R$.
807 \subsubsection{For $D = C$:}
809 $D \isin C$ and $D \le C$. OK.
811 \subsubsection{For $D \neq C, D \isin M$:}
813 Thus $D \le M$ so $D \le L$ and $D \le R$ so $D \isin L$ and $D \isin
814 R$. So by $\merge$, $D \isin C$. And $D \le C$. OK.
816 \subsubsection{For $D \neq C, D \not\isin M, D \isin X$:}
818 By $\merge$, $D \isin C$.
819 And $D \isin X$ means $D \le X$ so $D \le C$.
822 \subsubsection{For $D \neq C, D \not\isin M, D \not\isin L, D \not\isin R$:}
824 By $\merge$, $D \not\isin C$.
825 And $D \not\le L, D \not\le R$ so $D \not\le C$.