Save the show diff marks setting to app/local store

app/src/lib/stores/app-store.ts

@@ -7951,6 +7951,14 @@ export class AppStore extends TypedBaseStore<IAppState> {
       this.emitUpdate()
     }
   }
+
+  public _updateShowDiffCheckMarks(showDiffCheckMarks: boolean) {
+    if (showDiffCheckMarks !== this.showDiffCheckMarks) {
+      this.showDiffCheckMarks = showDiffCheckMarks
+      setBoolean(showDiffCheckMarksKey, showDiffCheckMarks)
+      this.emitUpdate()
+    }
+  }
 }
 
 /**

app/src/ui/dispatcher/dispatcher.ts

@@ -3917,4 +3917,8 @@ export class Dispatcher {
   public setUnderlineLinksSetting(underlineLinks: boolean) {
     return this.appStore._updateUnderlineLinks(underlineLinks)
   }
+
+  public setDiffCheckMarksSetting(diffCheckMarks: boolean) {
+    return this.appStore._updateShowDiffCheckMarks(diffCheckMarks)
+  }
 }

app/src/ui/preferences/preferences.tsx

@@ -682,6 +682,10 @@ export class Preferences extends React.Component<
 
     this.props.dispatcher.setUnderlineLinksSetting(this.state.underlineLinks)
 
+    this.props.dispatcher.setDiffCheckMarksSetting(
+      this.state.showDiffCheckMarks
+    )
+
     this.props.onDismissed()
   }