make switch to remove long-form gls

.gitignore

@@ -35,3 +35,4 @@ old
 *.slg
 *.slo
 *.sls
+.switch-*

glossary.tex

 \makeglossaries
 
+% We only want to show full descriptions (e.g. 'GM (Games Master)') in some books. These books make the file '.switch-gls', but most use nothing.
+\IfFileExists{.switch-gls}{
+  \setabbreviationstyle[acronym]{long-short-sc-desc}
+}{
+  \setabbreviationstyle[acronym]{nolong-short-sc}
+}
+
 \newacronym[
   description={The smallest unit of currency},
   shortplural={cp},