Add mutation to change fileByFile setting

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

@@ -28,6 +28,7 @@ export const SET_HIGHLIGHTED_ROW = 'SET_HIGHLIGHTED_ROW';
 export const SET_TREE_DATA = 'SET_TREE_DATA';
 export const SET_RENDER_TREE_LIST = 'SET_RENDER_TREE_LIST';
 export const SET_SHOW_WHITESPACE = 'SET_SHOW_WHITESPACE';
+export const SET_FILE_BY_FILE = 'SET_FILE_BY_FILE';
 export const TOGGLE_FILE_FINDER_VISIBLE = 'TOGGLE_FILE_FINDER_VISIBLE';
 
 export const REQUEST_FULL_DIFF = 'REQUEST_FULL_DIFF';

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

@@ -36,6 +36,7 @@ export default {
       projectPath,
       dismissEndpoint,
       showSuggestPopover,
+      viewDiffsFileByFile,
     } = options;
     Object.assign(state, {
       endpoint,
@@ -45,6 +46,7 @@ export default {
       projectPath,
       dismissEndpoint,
       showSuggestPopover,
+      viewDiffsFileByFile,
     });
   },
 
@@ -352,4 +354,7 @@ export default {
   [types.SET_SHOW_SUGGEST_POPOVER](state) {
     state.showSuggestPopover = false;
   },
+  [types.SET_FILE_BY_FILE](state, fileByFile) {
+    state.viewDiffsFileByFile = fileByFile;
+  },
 };

spec/frontend/diffs/store/mutations_spec.js

@@ -892,4 +892,18 @@ describe('DiffsStoreMutations', () => {
       expect(state.showSuggestPopover).toBe(false);
     });
   });
+
+  describe('SET_FILE_BY_FILE', () => {
+    it.each`
+      value    | opposite
+      ${true}  | ${false}
+      ${false} | ${true}
+    `('sets viewDiffsFileByFile to $value', ({ value, opposite }) => {
+      const state = { viewDiffsFileByFile: opposite };
+
+      mutations[types.SET_FILE_BY_FILE](state, value);
+
+      expect(state.viewDiffsFileByFile).toBe(value);
+    });
+  });
 });