Fix show full diff file not working with unified diffs

With unified diffs we only care about the inline diffs
However, when clicking show full file it ended up
creating a parallel array of diff lines.

app/assets/javascripts/diffs/components/diff_file_header.vue

@@ -10,6 +10,7 @@ import {
   GlDropdown,
   GlDropdownItem,
   GlDropdownDivider,
+  GlLoadingIcon,
 } from '@gitlab/ui';
 import ClipboardButton from '~/vue_shared/components/clipboard_button.vue';
 import FileIcon from '~/vue_shared/components/file_icon.vue';
@@ -32,6 +33,7 @@ export default {
     GlDropdown,
     GlDropdownItem,
     GlDropdownDivider,
+    GlLoadingIcon,
   },
   directives: {
     GlTooltip: GlTooltipDirective,
@@ -365,8 +367,10 @@ export default {
             <gl-dropdown-item
               v-if="!diffFile.is_fully_expanded"
               ref="expandDiffToFullFileButton"
+              :disabled="diffFile.isLoadingFullFile"
               @click="toggleFullDiff(diffFile.file_path)"
             >
+              <gl-loading-icon v-if="diffFile.isLoadingFullFile" inline />
               {{ expandDiffToFullFileTitle }}
             </gl-dropdown-item>
           </template>

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

@@ -536,15 +536,20 @@ export const setExpandedDiffLines = ({ commit, state }, { file, data }) => {
       }),
     }),
   };
+  const unifiedDiffLinesEnabled = window.gon?.features?.unifiedDiffLines;
   const currentDiffLinesKey =
-    state.diffViewType === INLINE_DIFF_VIEW_TYPE ? INLINE_DIFF_LINES_KEY : PARALLEL_DIFF_LINES_KEY;
+    state.diffViewType === INLINE_DIFF_VIEW_TYPE || unifiedDiffLinesEnabled
+      ? INLINE_DIFF_LINES_KEY
+      : PARALLEL_DIFF_LINES_KEY;
   const hiddenDiffLinesKey =
     state.diffViewType === INLINE_DIFF_VIEW_TYPE ? PARALLEL_DIFF_LINES_KEY : INLINE_DIFF_LINES_KEY;
 
-  commit(types.SET_HIDDEN_VIEW_DIFF_FILE_LINES, {
-    filePath: file.file_path,
-    lines: expandedDiffLines[hiddenDiffLinesKey],
-  });
+  if (!unifiedDiffLinesEnabled) {
+    commit(types.SET_HIDDEN_VIEW_DIFF_FILE_LINES, {
+      filePath: file.file_path,
+      lines: expandedDiffLines[hiddenDiffLinesKey],
+    });
+  }
 
   if (expandedDiffLines[currentDiffLinesKey].length > MAX_RENDERING_DIFF_LINES) {
     let index = START_RENDERING_INDEX;