Use git diff-tree for DiffFileTree on diff pages (#33514)

Modify Diff View FileTree to show all files

## Changes

* removes Show Status button on diff
* uses `git diff-tree` to generate the file tree for the diff
* doesn't reload the diff tree each time we load more files in the
preview
* selecting and unloaded file will keep loading until that file is
loaded
* removes `DiffFileList.vue` and "Show Stats" in diff options

## Open Questions

* selecting and unloaded file will keep loading until that file is
loaded. Is this behaviour okay? It matches what github does.

### Demo

In this demo I set `git.MAX_GIT_DIFF_FILES=1` in my `app.ini` to
demonstrate a worst case example. In most cases the behaviour isn't
nearly as jarring as we load a bunch of files at a time.


https://github.com/user-attachments/assets/72f29663-d6fc-472d-94fa-7fb5950c2836

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/components/DiffFileTree.vue

@@ -1,75 +1,18 @@
 <script lang="ts" setup>
-import DiffFileTreeItem, {type Item} from './DiffFileTreeItem.vue';
-import {loadMoreFiles} from '../features/repo-diff.ts';
+import DiffFileTreeItem from './DiffFileTreeItem.vue';
 import {toggleElem} from '../utils/dom.ts';
 import {diffTreeStore} from '../modules/stores.ts';
 import {setFileFolding} from '../features/file-fold.ts';
 import {computed, onMounted, onUnmounted} from 'vue';
+import {pathListToTree, mergeChildIfOnlyOneDir} from '../utils/filetree.ts';
 
 const LOCAL_STORAGE_KEY = 'diff_file_tree_visible';
 
 const store = diffTreeStore();
 
 const fileTree = computed(() => {
-  const result: Array<Item> = [];
-  for (const file of store.files) {
-    // Split file into directories
-    const splits = file.Name.split('/');
-    let index = 0;
-    let parent = null;
-    let isFile = false;
-    for (const split of splits) {
-      index += 1;
-      // reached the end
-      if (index === splits.length) {
-        isFile = true;
-      }
-      let newParent: Item = {
-        name: split,
-        children: [],
-        isFile,
-      };
-
-      if (isFile === true) {
-        newParent.file = file;
-      }
-
-      if (parent) {
-        // check if the folder already exists
-        const existingFolder = parent.children.find(
-          (x) => x.name === split,
-        );
-        if (existingFolder) {
-          newParent = existingFolder;
-        } else {
-          parent.children.push(newParent);
-        }
-      } else {
-        const existingFolder = result.find((x) => x.name === split);
-        if (existingFolder) {
-          newParent = existingFolder;
-        } else {
-          result.push(newParent);
-        }
-      }
-      parent = newParent;
-    }
-  }
-  const mergeChildIfOnlyOneDir = (entries: Array<Record<string, any>>) => {
-    for (const entry of entries) {
-      if (entry.children) {
-        mergeChildIfOnlyOneDir(entry.children);
-      }
-      if (entry.children.length === 1 && entry.children[0].isFile === false) {
-        // Merge it to the parent
-        entry.name = `${entry.name}/${entry.children[0].name}`;
-        entry.children = entry.children[0].children;
-      }
-    }
-  };
-  // Merge folders with just a folder as children in order to
-  // reduce the depth of our tree.
-  mergeChildIfOnlyOneDir(result);
+  const result = pathListToTree(store.files);
+  mergeChildIfOnlyOneDir(result); // mutation
   return result;
 });
 
@@ -121,19 +64,12 @@ function updateState(visible: boolean) {
   toggleElem(toShow, !visible);
   toggleElem(toHide, visible);
 }
-
-function loadMoreData() {
-  loadMoreFiles(store.linkLoadMore);
-}
 </script>
 
 <template>
   <div v-if="store.fileTreeIsVisible" class="diff-file-tree-items">
     <!-- only render the tree if we're visible. in many cases this is something that doesn't change very often -->
     <DiffFileTreeItem v-for="item in fileTree" :key="item.name" :item="item"/>
-    <div v-if="store.isIncomplete" class="tw-pt-1">
-      <a :class="['ui', 'basic', 'tiny', 'button', store.isLoadingNewData ? 'disabled' : '']" @click.stop="loadMoreData">{{ store.showMoreMessage }}</a>
-    </div>
   </div>
 </template>