Add a mutation to change the `viewer` of a diffFile

app/assets/javascripts/diffs/store/mutation_types.js

@@ -41,6 +41,8 @@ export const SET_CURRENT_VIEW_DIFF_FILE_LINES = 'SET_CURRENT_VIEW_DIFF_FILE_LINE
 export const ADD_CURRENT_VIEW_DIFF_FILE_LINES = 'ADD_CURRENT_VIEW_DIFF_FILE_LINES';
 export const TOGGLE_DIFF_FILE_RENDERING_MORE = 'TOGGLE_DIFF_FILE_RENDERING_MORE';
 
+export const SET_DIFF_FILE_VIEWER = 'SET_DIFF_FILE_VIEWER';
+
 export const SET_SHOW_SUGGEST_POPOVER = 'SET_SHOW_SUGGEST_POPOVER';
 
 export const TOGGLE_LINE_DISCUSSIONS = 'TOGGLE_LINE_DISCUSSIONS';

app/assets/javascripts/diffs/store/mutations.js

@@ -383,6 +383,11 @@ export default {
 
     file.renderingLines = !file.renderingLines;
   },
+  [types.SET_DIFF_FILE_VIEWER](state, { filePath, viewer }) {
+    const file = findDiffFile(state.diffFiles, filePath, 'file_path');
+
+    file.viewer = viewer;
+  },
   [types.SET_SHOW_SUGGEST_POPOVER](state) {
     state.showSuggestPopover = false;
   },