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 $L$ and $\pr$ as represented by $R^+, R^-$.
454 Construct $C$ which has $\pr$ removed.
455 Used for removing a branch dependency.
457 C \hasparents \{ L \}
459 \patchof{C} = \patchof{L}
461 \mergeof{C}{L}{R^+}{R^-}
464 \subsection{Conditions}
466 \[ \eqn{ Ingredients }{
467 R^+ \in \pry \land R^- = \baseof{R^+}
469 \[ \eqn{ Into Base }{
472 \[ \eqn{ Unique Tip }{
473 \pendsof{L}{\pry} = \{ R^+ \}
475 \[ \eqn{ Currently Included }{
479 \subsection{Ordering of ${L, R^+, R^-}$:}
481 By Unique Tip, $R^+ \le L$. By definition of $\base$, $R^- \le R^+$
482 so $R^- \le L$. So $R^+ \le C$ and $R^- \le C$.
485 (Note that $R^+ \not\le R^-$, i.e. the merge base
486 is a descendant, not an ancestor, of the 2nd parent.)
488 \subsection{No Replay}
490 No Replay for Merge Results applies. $\qed$
492 \subsection{Desired Contents}
494 \[ D \isin C \equiv [ D \notin \pry \land D \isin L ] \lor D = C \]
497 \subsubsection{For $D = C$:}
499 Trivially $D \isin C$. OK.
501 \subsubsection{For $D \neq C, D \not\le L$:}
503 By No Replay $D \not\isin L$. Also $D \not\le R^-$ hence
504 $D \not\isin R^-$. Thus $D \not\isin C$. OK.
506 \subsubsection{For $D \neq C, D \le L, D \in \pry$:}
508 By Currently Included, $D \isin L$.
510 By Tip Self Inpatch, $D \isin R^+ \equiv D \le R^+$, but by
511 by Unique Tip, $D \le R^+ \equiv D \le L$.
514 By Base Acyclic, $D \not\isin R^-$.
516 Apply $\merge$: $D \not\isin C$. OK.
518 \subsubsection{For $D \neq C, D \le L, D \notin \pry$:}
520 By Tip Contents for $R^+$, $D \isin R^+ \equiv D \isin R^-$.
522 Apply $\merge$: $D \isin C \equiv D \isin L$. OK.
526 \subsection{Unique Base}
528 Into Base means that $C \in \pn$, so Unique Base is not
531 \subsection{Tip Contents}
533 Again, not applicable. $\qed$
535 \subsection{Base Acyclic}
537 By Base Acyclic for $L$, $D \isin L \implies D \not\in \py$.
538 And by Into Base $C \not\in \py$.
539 Now from Desired Contents, above, $D \isin C
540 \implies D \isin L \lor D = C$, which thus
541 $\implies D \not\in \py$. $\qed$.
543 \subsection{Coherence and Patch Inclusion}
545 Need to consider some $D \in \py$. By Into Base, $D \neq C$.
547 \subsubsection{For $\p = \pr$:}
548 By Desired Contents, above, $D \not\isin C$.
549 So $C \nothaspatch \pr$.
551 \subsubsection{For $\p \neq \pr$:}
552 By Desired Contents, $D \isin C \equiv D \isin L$
553 (since $D \in \py$ so $D \not\in \pry$).
555 If $L \nothaspatch \p$, $D \not\isin L$ so $D \not\isin C$.
556 So $L \nothaspatch \p \implies C \nothaspatch \p$.
558 Whereas if $L \haspatch \p$, $D \isin L \equiv D \le L$.
559 so $L \haspatch \p \implies C \haspatch \p$.
563 \section{Foreign Inclusion}
565 Consider some $D$ s.t. $\patchof{D} = \bot$. $D \neq C$.
566 So by Desired Contents $D \isin C \equiv D \isin L$.
567 By Foreign Inclusion of $D$ in $L$, $D \isin L \equiv D \le L$.
569 And $D \le C \equiv D \le L$.
570 Thus $D \isin C \equiv D \le C$.
576 Merge commits $L$ and $R$ using merge base $M$:
578 C \hasparents \{ L, R \}
580 \patchof{C} = \patchof{L}
584 We will occasionally use $X,Y$ s.t. $\{X,Y\} = \{L,R\}$.
586 \subsection{Conditions}
587 \[ \eqn{ Ingredients }{
590 \[ \eqn{ Tip Merge }{
593 R \in \py : & \baseof{R} \ge \baseof{L}
594 \land [\baseof{L} = M \lor \baseof{L} = \baseof{M}] \\
595 R \in \pn : & M = \baseof{L} \\
596 \text{otherwise} : & \false
599 \[ \eqn{ Merge Acyclic }{
604 \[ \eqn{ Removal Merge Ends }{
605 X \not\haspatch \p \land
609 \pendsof{Y}{\py} = \pendsof{M}{\py}
611 \[ \eqn{ Addition Merge Ends }{
612 X \not\haspatch \p \land
616 \bigforall_{E \in \pendsof{X}{\py}} E \le Y
620 \subsection{Non-Topbloke merges}
622 We require both $\patchof{L} = \bot$ and $\patchof{R} = \bot$.
623 I.e. not only is it forbidden to merge into a Topbloke-controlled
624 branch without Topbloke's assistance, it is also forbidden to
625 merge any Topbloke-controlled branch into any plain git branch.
627 Given those conditions, Tip Merge and Merge Acyclic do not apply.
628 And $Y \not\in \py$ so $\neg [ Y \haspatch \p ]$ so neither
629 Merge Ends condition applies. Good.
631 \subsection{No Replay}
633 No Replay for Merge Results applies. $\qed$
635 \subsection{Unique Base}
637 Need to consider only $C \in \py$, ie $L \in \py$,
638 and calculate $\pendsof{C}{\pn}$. So we will consider some
639 putative ancestor $A \in \pn$ and see whether $A \le C$.
641 By Exact Ancestors for C, $A \le C \equiv A \le L \lor A \le R \lor A = C$.
642 But $C \in py$ and $A \in \pn$ so $A \neq C$.
643 Thus $A \le C \equiv A \le L \lor A \le R$.
645 By Unique Base of L and Transitive Ancestors,
646 $A \le L \equiv A \le \baseof{L}$.
648 \subsubsection{For $R \in \py$:}
650 By Unique Base of $R$ and Transitive Ancestors,
651 $A \le R \equiv A \le \baseof{R}$.
653 But by Tip Merge condition on $\baseof{R}$,
654 $A \le \baseof{L} \implies A \le \baseof{R}$, so
655 $A \le \baseof{R} \lor A \le \baseof{L} \equiv A \le \baseof{R}$.
656 Thus $A \le C \equiv A \le \baseof{R}$.
657 That is, $\baseof{C} = \baseof{R}$.
659 \subsubsection{For $R \in \pn$:}
661 By Tip Merge condition on $R$ and since $M \le R$,
662 $A \le \baseof{L} \implies A \le R$, so
663 $A \le R \lor A \le \baseof{L} \equiv A \le R$.
664 Thus $A \le C \equiv A \le R$.
665 That is, $\baseof{C} = R$.
669 \subsection{Coherence and Patch Inclusion}
671 Need to determine $C \haspatch \p$ based on $L,M,R \haspatch \p$.
672 This involves considering $D \in \py$.
674 \subsubsection{For $L \nothaspatch \p, R \nothaspatch \p$:}
675 $D \not\isin L \land D \not\isin R$. $C \not\in \py$ (otherwise $L
676 \in \py$ ie $L \haspatch \p$ by Tip Self Inpatch). So $D \neq C$.
677 Applying $\merge$ gives $D \not\isin C$ i.e. $C \nothaspatch \p$.
679 \subsubsection{For $L \haspatch \p, R \haspatch \p$:}
680 $D \isin L \equiv D \le L$ and $D \isin R \equiv D \le R$.
681 (Likewise $D \isin X \equiv D \le X$ and $D \isin Y \equiv D \le Y$.)
683 Consider $D = C$: $D \isin C$, $D \le C$, OK for $C \haspatch \p$.
685 For $D \neq C$: $D \le C \equiv D \le L \lor D \le R
686 \equiv D \isin L \lor D \isin R$.
687 (Likewise $D \le C \equiv D \le X \lor D \le Y$.)
689 Consider $D \neq C, D \isin X \land D \isin Y$:
690 By $\merge$, $D \isin C$. Also $D \le X$
691 so $D \le C$. OK for $C \haspatch \p$.
693 Consider $D \neq C, D \not\isin X \land D \not\isin Y$:
694 By $\merge$, $D \not\isin C$.
695 And $D \not\le X \land D \not\le Y$ so $D \not\le C$.
696 OK for $C \haspatch \p$.
698 Remaining case, wlog, is $D \not\isin X \land D \isin Y$.
699 $D \not\le X$ so $D \not\le M$ so $D \not\isin M$.
700 Thus by $\merge$, $D \isin C$. And $D \le Y$ so $D \le C$.
701 OK for $C \haspatch \p$.
703 So indeed $L \haspatch \p \land R \haspatch \p \implies C \haspatch \p$.
705 \subsubsection{For (wlog) $X \not\haspatch \p, Y \haspatch \p$:}
707 $M \haspatch \p \implies C \nothaspatch \p$.
708 $M \nothaspatch \p \implies C \haspatch \p$.
712 One of the Merge Ends conditions applies.
713 Recall that we are considering $D \in \py$.
714 $D \isin Y \equiv D \le Y$. $D \not\isin X$.
715 We will show for each of
716 various cases that $D \isin C \equiv M \nothaspatch \p \land D \le C$
717 (which suffices by definition of $\haspatch$ and $\nothaspatch$).
719 Consider $D = C$: Thus $C \in \py, L \in \py$, and by Tip
720 Self Inpatch $L \haspatch \p$, so $L=Y, R=X$. By Tip Merge,
721 $M=\baseof{L}$. So by Base Acyclic $D \not\isin M$, i.e.
722 $M \nothaspatch \p$. And indeed $D \isin C$ and $D \le C$. OK.
724 Consider $D \neq C, M \nothaspatch P, D \isin Y$:
725 $D \le Y$ so $D \le C$.
726 $D \not\isin M$ so by $\merge$, $D \isin C$. OK.
728 Consider $D \neq C, M \nothaspatch P, D \not\isin Y$:
729 $D \not\le Y$. If $D \le X$ then
730 $D \in \pancsof{X}{\py}$, so by Addition Merge Ends and
731 Transitive Ancestors $D \le Y$ --- a contradiction, so $D \not\le X$.
732 Thus $D \not\le C$. By $\merge$, $D \not\isin C$. OK.
734 Consider $D \neq C, M \haspatch P, D \isin Y$:
735 $D \le Y$ so $D \in \pancsof{Y}{\py}$ so by Removal Merge Ends
736 and Transitive Ancestors $D \in \pancsof{M}{\py}$ so $D \le M$.
737 Thus $D \isin M$. By $\merge$, $D \not\isin C$. OK.
739 Consider $D \neq C, M \haspatch P, D \not\isin Y$:
740 By $\merge$, $D \not\isin C$. OK.
744 \subsection{Base Acyclic}
746 This applies when $C \in \pn$.
747 $C \in \pn$ when $L \in \pn$ so by Merge Acyclic, $R \nothaspatch \p$.
749 Consider some $D \in \py$.
751 By Base Acyclic of $L$, $D \not\isin L$. By the above, $D \not\isin
752 R$. And $D \neq C$. So $D \not\isin C$.
756 \subsection{Tip Contents}
758 We need worry only about $C \in \py$.
759 And $\patchof{C} = \patchof{L}$
760 so $L \in \py$ so $L \haspatch \p$. We will use the Unique Base
761 of $C$, and its Coherence and Patch Inclusion, as just proved.
763 Firstly we show $C \haspatch \p$: If $R \in \py$, then $R \haspatch
764 \p$ and by Coherence/Inclusion $C \haspatch \p$ . If $R \not\in \py$
765 then by Tip Merge $M = \baseof{L}$ so by Base Acyclic and definition
766 of $\nothaspatch$, $M \nothaspatch \p$. So by Coherence/Inclusion $C
767 \haspatch \p$ (whether $R \haspatch \p$ or $\nothaspatch$).
769 We will consider an arbitrary commit $D$
770 and prove the Exclusive Tip Contents form.
772 \subsubsection{For $D \in \py$:}
773 $C \haspatch \p$ so by definition of $\haspatch$, $D \isin C \equiv D
776 \subsubsection{For $D \not\in \py, R \not\in \py$:}
778 $D \neq C$. By Tip Contents of $L$,
779 $D \isin L \equiv D \isin \baseof{L}$, and by Tip Merge condition,
780 $D \isin L \equiv D \isin M$. So by definition of $\merge$, $D \isin
781 C \equiv D \isin R$. And $R = \baseof{C}$ by Unique Base of $C$.
782 Thus $D \isin C \equiv D \isin \baseof{C}$. OK.
784 \subsubsection{For $D \not\in \py, R \in \py$:}
789 $D \isin L \equiv D \isin \baseof{L}$ and
790 $D \isin R \equiv D \isin \baseof{R}$.
792 If $\baseof{L} = M$, trivially $D \isin M \equiv D \isin \baseof{L}.$
793 Whereas if $\baseof{L} = \baseof{M}$, by definition of $\base$,
794 $\patchof{M} = \patchof{L} = \py$, so by Tip Contents of $M$,
795 $D \isin M \equiv D \isin \baseof{M} \equiv D \isin \baseof{L}$.
797 So $D \isin M \equiv D \isin L$ and by $\merge$,
798 $D \isin C \equiv D \isin R$. But from Unique Base,
799 $\baseof{C} = R$ so $D \isin C \equiv D \isin \baseof{C}$. OK.
803 \subsection{Foreign Inclusion}
805 Consider some $D$ s.t. $\patchof{D} = \bot$.
806 By Foreign Inclusion of $L, M, R$:
807 $D \isin L \equiv D \le L$;
808 $D \isin M \equiv D \le M$;
809 $D \isin R \equiv D \le R$.
811 \subsubsection{For $D = C$:}
813 $D \isin C$ and $D \le C$. OK.
815 \subsubsection{For $D \neq C, D \isin M$:}
817 Thus $D \le M$ so $D \le L$ and $D \le R$ so $D \isin L$ and $D \isin
818 R$. So by $\merge$, $D \isin C$. And $D \le C$. OK.
820 \subsubsection{For $D \neq C, D \not\isin M, D \isin X$:}
822 By $\merge$, $D \isin C$.
823 And $D \isin X$ means $D \le X$ so $D \le C$.
826 \subsubsection{For $D \neq C, D \not\isin M, D \not\isin L, D \not\isin R$:}
828 By $\merge$, $D \not\isin C$.
829 And $D \not\le L, D \not\le R$ so $D \not\le C$.