\documentclass[a4paper]{strayman}
\let\numberwithin=\notdef
\usepackage{MnSymbol}
\usepackage{stmaryrd}
\usepackage{slashed}
\usepackage{txfonts}
\usepackage{amsfonts}
%\usepackage{accents}

\renewcommand{\ge}{\geqslant}
\renewcommand{\le}{\leqslant}

\newcommand{\has}{\sqsupseteq}
\newcommand{\isin}{\sqsubseteq}

\newcommand{\nothaspatch}{{%
  \declareslashed{}{\sslash}{-0.04}{0}{\Sqsupset}\slashed{\Sqsupset}}}
\newcommand{\notpatchisin}{{%
  \declareslashed{}{\sslash}{-0.04}{0}{\Sqsubset}\slashed{\Sqsubset}}}
\newcommand{\haspatch}{\Sqsupset}
\newcommand{\patchisin}{\Sqsubset}

\newcommand{\set}[1]{\mathbb #1}
\newcommand{\pa}[1]{\varmathbb #1}
\newcommand{\pay}[1]{\pa{#1}^+}
\newcommand{\pan}[1]{\pa{#1}^-}

\newcommand{\p}{\pa{P}}
\newcommand{\py}{\pay{P}}
\newcommand{\pn}{\pan{P}}

%\newcommand{\hasparents}{\underaccent{1}{>}}
%\newcommand{\hasparents}{{%
%  \declareslashed{}{_{_1}}{0}{-0.8}{>}\slashed{>}}}
\newcommand{\hasparents}{>_{\mkern-7.0mu _1}}
\newcommand{\areparents}{<_{\mkern-14.0mu _1\mkern+5.0mu}}

\renewcommand{\implies}{\Rightarrow}

\begin{document}

\section{Notation}

$ C \hasparents \set X $ The parents of commit $C$ are exactly the set
$\set X$.

$ C \ge D $ $C$ is a descendant of $D$ in the git commit
graph.  This is a partial order, namely the transitive closure of 
$ D \in \set X $ where $ C \hasparents \set X $.

$ C \has D $ Informally, the tree at commit $C$ contains the change
made in commit $D$.  Does not take account of deliberate reversions by
the user or in non-Topbloke-controlled branches; these are considered
normal, forward, commits.  For merges and Topbloke-generated
anticommits, the ``change made'' is only to be thought of as any
conflict resolution.  This is not a partial order because it is not
transitive.

\section{Invariants}

No rewind/replay: $ C \has D \implies C \ge D $

\end{document}
