add restate package that provides mechanics to restate theorems if they are not part of the current document

wip/mkessler-restate.sty

@@ -0,0 +1,37 @@
+\NeedsTeXFormat{LaTeX2e}
+\ProvidesPackage{mkessler-restate}
+
+\RequirePackage{xkeyval}
+
+\newif\ifmkessler@restate@english\mkessler@restate@englishtrue
+\DeclareOptionX{english}{\mkessler@restate@englishtrue}
+\DeclareOptionX{german}{\mkessler@restate@englishfalse}
+\DeclareOptionX{ngerman}{\mkessler@restate@englishfalse}
+
+\define@boolkey+{mkessler-restate.sty}[mkessler@restate@]{strict}[true]{
+    \ifmkessler@restate@strict
+        \PackageInfo{mkessler-restate}{Strict mode enabled. Undefined restates will throw errors.}%
+    \else
+        \PackageInfo{mkessler-restate}{Strict mode disabled. Undefined restates will now print placeholder boxes}%
+    \fi
+}{
+    \PackageWarning{mkessler-restate}{Erroneous input to key 'strict' ignored. Provide =true or =false.}
+}
+\ProcessOptionsX*\relax
+
+\newcommand\restatesetup[1]{\setkeys{mkessler-restate.sty}{#1}}
+
+\RequirePackage{todonotes}
+\RequirePackage{xparse}
+
+\NewDocumentCommand{\restatetheorem}{s m}{
+    \ifcsdef{#2}{
+        \ifx#1\BooleanTrue\csname#2\endcsname*\else\csname#2\endcsname\fi
+    }{
+    \ifmkessler@restate@strict
+    \PackageError{mkessler-restate}{Strict mode enabled but restate command not defined}{The theorem you tried to restate is not defined. Either make sure it is so that it can be printed or disable the strict mode with \noexpand\restatesetup{strict=false} to print a placeholder instead}
+    \else
+    \missingfigure{\ifmkessler@restate@english Here theorem #1 is missing, since it is not part of this document.\else Hier fehlt die Wiederholung von Satz #1, der nicht Teil dieses Dokumentes ist.\fi}
+    \fi
+    }
+}