Add filetree on left of diff view (#21012)

This PR adds a filetree to the left side of the files/diff view.

Initially the filetree will not be shown and may be shown via a new
"Show file tree" button.

Showing and hiding is using the same icon as github. Folders are
collapsible. On small devices (max-width 991 PX) the file tree will be
hidden.

Close #18192

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

13 files changed, 590 insertions, 158 deletions

diff --git a/templates/repo/commit_page.tmpl b/templates/repo/commit_page.tmpl
index 8ece768832..da37aaa9b3 100644
--- a/templates/repo/commit_page.tmpl
+++ b/templates/repo/commit_page.tmpl
@@ -1,7 +1,7 @@
 {{template "base/head" .}}
 <div class="page-content repository diff">
 	{{template "repo/header" .}}
-	<div class="ui container {{if .IsSplitStyle}}fluid padded{{end}}">
+	<div class="ui container fluid padded">
 		{{$class := ""}}
 		{{if .Commit.Signature}}
 			{{$class = (printf "%s%s" $class " isSigned")}}
diff --git a/templates/repo/diff/box.tmpl b/templates/repo/diff/box.tmpl
index 51769eb953..4624a53ba3 100644
--- a/templates/repo/diff/box.tmpl
+++ b/templates/repo/diff/box.tmpl
@@ -14,6 +14,11 @@
 {{else}}
 	<div>
 		<div class="diff-detail-box diff-box sticky df sb ac fw">
+			<a class="diff-toggle-file-tree-button">
+				{{/* the icon meaning is reversed here, "octicon-sidebar-collapse" means show the file tree */}}
+				{{svg "octicon-sidebar-collapse" 16 "icon hide"}}
+				{{svg "octicon-sidebar-expand" 16 "icon"}}
+			</a>
 			<div class="diff-detail-stats df ac">
 				{{svg "octicon-diff" 16 "mr-2"}}{{.locale.Tr "repo.diff.stats_desc" .Diff.NumFiles .Diff.TotalAddition .Diff.TotalDeletion | Str2html}}
 			</div>
@@ -31,145 +36,151 @@
 				{{end}}
 			</div>
 		</div>
-		<ol class="diff-detail-box diff-stats m-0 hide" id="diff-files">
-			{{range .Diff.Files}}
-				<li>
-					<div class="bold df ac pull-right">
-						{{if .IsBin}}
-							<span class="ml-1 mr-3">
-								{{$.locale.Tr "repo.diff.bin"}}
-							</span>
-						{{else}}
-							{{template "repo/diff/stats" dict "file" . "root" $}}
-						{{end}}
-					</div>
-					<!-- todo finish all file status, now modify, add, delete and rename -->
-					<span class="status {{DiffTypeToStr .GetType}} tooltip" data-content="{{DiffTypeToStr .GetType}}" data-position="right center">&nbsp;</span>
-					<a class="file mono" href="#diff-{{.NameHash}}">{{.Name}}</a>
-				</li>
-			{{end}}
-			{{if .Diff.IsIncomplete}}
-				<li id="diff-too-many-files-stats" class="pt-2">
-					<span class="file df ac sb">{{$.locale.Tr "repo.diff.too_many_files"}}
-						<a class="ui basic tiny button" id="diff-show-more-files-stats" data-href="{{$.Link}}?skip-to={{.Diff.End}}&file-only=true">{{.locale.Tr "repo.diff.show_more"}}</a>
-					</span>
-				</li>
-			{{end}}
-		</ol>
-		<div id="diff-file-boxes">
-			{{range $file := .Diff.Files}}
-				{{/*notice: the index of Diff.Files should not be used for element ID, because the index will be restarted from 0 when doing load-more for PRs with a lot of files*/}}
-				{{$blobBase := call $.GetBlobByPathForCommit $.BaseCommit $file.OldName}}
-				{{$blobHead := call $.GetBlobByPathForCommit $.HeadCommit $file.Name}}
-				{{$isImage := or (call $.IsBlobAnImage $blobBase) (call $.IsBlobAnImage $blobHead)}}
-				{{$isCsv := (call $.IsCsvFile $file)}}
-				{{$showFileViewToggle := or $isImage (and (not $file.IsIncomplete) $isCsv)}}
-				<div class="diff-file-box diff-box file-content {{TabSizeClass $.Editorconfig $file.Name}} mt-3" id="diff-{{$file.NameHash}}" data-old-filename="{{$file.OldName}}" data-new-filename="{{$file.Name}}" {{if $file.ShouldBeHidden}}data-folded="true"{{end}}>
-					<h4 class="diff-file-header sticky-2nd-row ui top attached normal header df ac sb">
-						<div class="df ac">
-							<a role="button" class="fold-file muted mr-2">
-								{{if $file.ShouldBeHidden}}
-									{{svg "octicon-chevron-right" 18}}
-								{{else}}
-									{{svg "octicon-chevron-down" 18}}
-								{{end}}
-							</a>
-							<div class="bold df ac">
-								{{if $file.IsBin}}
-									<span class="ml-1 mr-3">
-										{{$.locale.Tr "repo.diff.bin"}}
-									</span>
-								{{else}}
-									{{template "repo/diff/stats" dict "file" . "root" $}}
-								{{end}}
-							</div>
-							<span class="file mono"><a class="muted" href="#diff-{{$file.NameHash}}">{{if $file.IsRenamed}}{{$file.OldName}} &rarr; {{end}}{{$file.Name}}</a>{{if .IsLFSFile}} ({{$.locale.Tr "repo.stored_lfs"}}){{end}}</span>
-							{{if $file.IsGenerated}}
-								<span class="ui label ml-3">{{$.locale.Tr "repo.diff.generated"}}</span>
-							{{end}}
-							{{if $file.IsVendored}}
-								<span class="ui label ml-3">{{$.locale.Tr "repo.diff.vendored"}}</span>
-							{{end}}
-						</div>
-						<div class="diff-file-header-actions df ac">
-							{{if $showFileViewToggle}}
-								<div class="ui compact icon buttons">
-									<span class="ui tiny basic button tooltip file-view-toggle" data-toggle-selector="#diff-source-{{$file.NameHash}}" data-content="{{$.locale.Tr "repo.file_view_source"}}" data-position="bottom center">{{svg "octicon-code"}}</span>
-									<span class="ui tiny basic button tooltip file-view-toggle active" data-toggle-selector="#diff-rendered-{{$file.NameHash}}" data-content="{{$.locale.Tr "repo.file_view_rendered"}}" data-position="bottom center">{{svg "octicon-file"}}</span>
-								</div>
-							{{end}}
-							{{if $file.IsProtected}}
-								<span class="ui basic label">{{$.locale.Tr "repo.diff.protected"}}</span>
-							{{end}}
-							{{if not (or $file.IsIncomplete $file.IsBin $file.IsSubmodule)}}
-								<a class="ui basic tiny button unescape-button">{{$.locale.Tr "repo.unescape_control_characters"}}</a>
-								<a class="ui basic tiny button escape-button" style="display: none;">{{$.locale.Tr "repo.escape_control_characters"}}</a>
-							{{end}}
-							{{if and (not $file.IsSubmodule) (not $.PageIsWiki)}}
-								{{if $file.IsDeleted}}
-									<a class="ui basic tiny button" rel="nofollow" href="{{$.BeforeSourcePath}}/{{PathEscapeSegments .Name}}">{{$.locale.Tr "repo.diff.view_file"}}</a>
-								{{else}}
-									<a class="ui basic tiny button" rel="nofollow" href="{{$.SourcePath}}/{{PathEscapeSegments .Name}}">{{$.locale.Tr "repo.diff.view_file"}}</a>
-								{{end}}
-							{{end}}
-							{{if and $.IsSigned $.PageIsPullFiles (not $.IsArchived)}}
-								{{if $file.HasChangedSinceLastReview}}
-									<span class="changed-since-last-review unselectable">{{$.locale.Tr "repo.pulls.has_changed_since_last_review"}}</span>
-								{{end}}
-								<label data-link="{{$.Issue.Link}}/viewed-files" data-headcommit="{{$.PullHeadCommitID}}" class="viewed-file-form unselectable{{if $file.IsViewed}} viewed-file-checked-form{{end}}">
-									<input type="checkbox" name="{{$file.GetDiffFileName}}" autocomplete="off"{{if $file.IsViewed}} checked{{end}}> {{$.locale.Tr "repo.pulls.has_viewed_file"}}
-								</label>
-							{{end}}
-						</div>
-					</h4>
-					<div class="diff-file-body ui attached unstackable table segment" {{if $file.IsViewed}}data-folded="true"{{end}}>
-						<div id="diff-source-{{$file.NameHash}}" class="file-body file-code unicode-escaped code-diff{{if $.IsSplitStyle}} code-diff-split{{else}} code-diff-unified{{end}}{{if $showFileViewToggle}} hide{{end}}">
-							{{if or $file.IsIncomplete $file.IsBin}}
-								<div class="diff-file-body binary" style="padding: 5px 10px;">
-									{{if $file.IsIncomplete}}
-										{{if $file.IsIncompleteLineTooLong}}
-											{{$.locale.Tr "repo.diff.file_suppressed_line_too_long"}}
+		<script id="diff-data-script">
+				(() => {
+					const diffData = {
+						files: [{{range $i, $file := .Diff.Files}}{Name:"{{$file.Name}}",NameHash:"{{$file.NameHash}}",Type:{{$file.Type}},IsBin:{{$file.IsBin}},Addition:{{$file.Addition}},Deletion:{{$file.Deletion}}},{{end}}],
+						isIncomplete: {{.Diff.IsIncomplete}},
+						tooManyFilesMessage: "{{$.locale.Tr "repo.diff.too_many_files"}}",
+						binaryFileMessage: "{{$.locale.Tr "repo.diff.bin"}}",
+						showMoreMessage: "{{.locale.Tr "repo.diff.show_more"}}",
+						statisticsMessage: "{{.locale.Tr "repo.diff.stats_desc_file"}}",
+						fileTreeIsVisible: false,
+						fileListIsVisible: false,
+						isLoadingNewData: false,
+						diffEnd: {{.Diff.End}},
+						link: "{{$.Link}}"
+					};
+					if(window.config.pageData.diffFileInfo) {
+						// Page is already loaded - add the data to our existing data
+						window.config.pageData.diffFileInfo.files.push(...diffData.files);
+						window.config.pageData.diffFileInfo.isIncomplete = diffData.isIncomplete;
+						window.config.pageData.diffFileInfo.diffEnd = diffData.diffEnd;
+						window.config.pageData.diffFileInfo.link = diffData.link;
+					} else {
+						// new load of page - populate initial data
+						window.config.pageData.diffFileInfo = diffData;
+					}
+				})();
+				</script>
+		<div id="diff-file-list-container"></div>
+		<div id="diff-container">
+				<div id="diff-file-tree-container"></div>
+				<div id="diff-file-boxes" class="sixteen wide column">
+					{{range $i, $file := .Diff.Files}}
+						{{/*notice: the index of Diff.Files should not be used for element ID, because the index will be restarted from 0 when doing load-more for PRs with a lot of files*/}}
+						{{$blobBase := call $.GetBlobByPathForCommit $.BaseCommit $file.OldName}}
+						{{$blobHead := call $.GetBlobByPathForCommit $.HeadCommit $file.Name}}
+						{{$isImage := or (call $.IsBlobAnImage $blobBase) (call $.IsBlobAnImage $blobHead)}}
+						{{$isCsv := (call $.IsCsvFile $file)}}
+						{{$showFileViewToggle := or $isImage (and (not $file.IsIncomplete) $isCsv)}}
+						<div class="diff-file-box diff-box file-content {{TabSizeClass $.Editorconfig $file.Name}} mt-3" id="diff-{{$file.NameHash}}" data-old-filename="{{$file.OldName}}" data-new-filename="{{$file.Name}}" {{if $file.ShouldBeHidden}}data-folded="true"{{end}}>
+							<h4 class="diff-file-header sticky-2nd-row ui top attached normal header df ac sb">
+								<div class="df ac">
+									<a role="button" class="fold-file muted mr-2">
+										{{if $file.ShouldBeHidden}}
+											{{svg "octicon-chevron-right" 18}}
 										{{else}}
-											{{$.locale.Tr "repo.diff.file_suppressed"}}
-											<a class="ui basic tiny button diff-show-more-button" data-href="{{$.Link}}?file-only=true&files={{$file.Name}}&files={{$file.OldName}}">{{$.locale.Tr "repo.diff.load"}}</a>
+											{{svg "octicon-chevron-down" 18}}
 										{{end}}
-									{{else}}
-										{{$.locale.Tr "repo.diff.bin_not_shown"}}
+									</a>
+									<div class="bold df ac">
+										{{if $file.IsBin}}
+											<span class="ml-1 mr-3">
+												{{$.locale.Tr "repo.diff.bin"}}
+											</span>
+										{{else}}
+											{{template "repo/diff/stats" dict "file" . "root" $}}
+										{{end}}
+									</div>
+									<span class="file mono"><a class="muted" href="#diff-{{$file.NameHash}}">{{if $file.IsRenamed}}{{$file.OldName}} &rarr; {{end}}{{$file.Name}}</a>{{if .IsLFSFile}} ({{$.locale.Tr "repo.stored_lfs"}}){{end}}</span>
+									{{if $file.IsGenerated}}
+										<span class="ui label ml-3">{{$.locale.Tr "repo.diff.generated"}}</span>
+									{{end}}
+									{{if $file.IsVendored}}
+										<span class="ui label ml-3">{{$.locale.Tr "repo.diff.vendored"}}</span>
 									{{end}}
 								</div>
-							{{else}}
-								<table class="chroma" data-new-comment-url="{{$.Issue.HTMLURL}}/files/reviews/new_comment" data-path="{{$file.Name}}">
-									{{if $.IsSplitStyle}}
-										{{template "repo/diff/section_split" dict "file" . "root" $}}
-									{{else}}
-										{{template "repo/diff/section_unified" dict "file" . "root" $}}
+								<div class="diff-file-header-actions df ac">
+									{{if $showFileViewToggle}}
+										<div class="ui compact icon buttons">
+											<span class="ui tiny basic button tooltip file-view-toggle" data-toggle-selector="#diff-source-{{$file.NameHash}}" data-content="{{$.locale.Tr "repo.file_view_source"}}" data-position="bottom center">{{svg "octicon-code"}}</span>
+											<span class="ui tiny basic button tooltip file-view-toggle active" data-toggle-selector="#diff-rendered-{{$file.NameHash}}" data-content="{{$.locale.Tr "repo.file_view_rendered"}}" data-position="bottom center">{{svg "octicon-file"}}</span>
+										</div>
 									{{end}}
-								</table>
-							{{end}}
-						</div>
-						{{if $showFileViewToggle}}
-							<div id="diff-rendered-{{$file.NameHash}}" class="file-body file-code {{if $.IsSplitStyle}} code-diff-split{{else}} code-diff-unified{{end}}">
-								<table class="chroma w-100">
-									{{if $isImage}}
-										{{template "repo/diff/image_diff" dict "file" . "root" $ "blobBase" $blobBase "blobHead" $blobHead}}
+									{{if $file.IsProtected}}
+										<span class="ui basic label">{{$.locale.Tr "repo.diff.protected"}}</span>
+									{{end}}
+									{{if not (or $file.IsIncomplete $file.IsBin $file.IsSubmodule)}}
+										<a class="ui basic tiny button unescape-button">{{$.locale.Tr "repo.unescape_control_characters"}}</a>
+										<a class="ui basic tiny button escape-button" style="display: none;">{{$.locale.Tr "repo.escape_control_characters"}}</a>
+									{{end}}
+									{{if and (not $file.IsSubmodule) (not $.PageIsWiki)}}
+										{{if $file.IsDeleted}}
+											<a class="ui basic tiny button" rel="nofollow" href="{{$.BeforeSourcePath}}/{{PathEscapeSegments .Name}}">{{$.locale.Tr "repo.diff.view_file"}}</a>
+										{{else}}
+											<a class="ui basic tiny button" rel="nofollow" href="{{$.SourcePath}}/{{PathEscapeSegments .Name}}">{{$.locale.Tr "repo.diff.view_file"}}</a>
+										{{end}}
+									{{end}}
+									{{if and $.IsSigned $.PageIsPullFiles (not $.IsArchived)}}
+										{{if $file.HasChangedSinceLastReview}}
+											<span class="changed-since-last-review unselectable">{{$.locale.Tr "repo.pulls.has_changed_since_last_review"}}</span>
+										{{end}}
+										<label data-link="{{$.Issue.Link}}/viewed-files" data-headcommit="{{$.PullHeadCommitID}}" class="viewed-file-form unselectable{{if $file.IsViewed}} viewed-file-checked-form{{end}}">
+											<input type="checkbox" name="{{$file.GetDiffFileName}}" autocomplete="off"{{if $file.IsViewed}} checked{{end}}> {{$.locale.Tr "repo.pulls.has_viewed_file"}}
+										</label>
+									{{end}}
+								</div>
+							</h4>
+							<div class="diff-file-body ui attached unstackable table segment" {{if $file.IsViewed}}data-folded="true"{{end}}>
+								<div id="diff-source-{{$file.NameHash}}" class="file-body file-code unicode-escaped code-diff{{if $.IsSplitStyle}} code-diff-split{{else}} code-diff-unified{{end}}{{if $showFileViewToggle}} hide{{end}}">
+									{{if or $file.IsIncomplete $file.IsBin}}
+										<div class="diff-file-body binary" style="padding: 5px 10px;">
+											{{if $file.IsIncomplete}}
+												{{if $file.IsIncompleteLineTooLong}}
+													{{$.locale.Tr "repo.diff.file_suppressed_line_too_long"}}
+												{{else}}
+													{{$.locale.Tr "repo.diff.file_suppressed"}}
+													<a class="ui basic tiny button diff-show-more-button" data-href="{{$.Link}}?file-only=true&files={{$file.Name}}&files={{$file.OldName}}">{{$.locale.Tr "repo.diff.load"}}</a>
+												{{end}}
+											{{else}}
+												{{$.locale.Tr "repo.diff.bin_not_shown"}}
+											{{end}}
+										</div>
 									{{else}}
-										{{template "repo/diff/csv_diff" dict "file" . "root" $ "blobBase" $blobBase "blobHead" $blobHead}}
+										<table class="chroma" data-new-comment-url="{{$.Issue.HTMLURL}}/files/reviews/new_comment" data-path="{{$file.Name}}">
+											{{if $.IsSplitStyle}}
+												{{template "repo/diff/section_split" dict "file" . "root" $}}
+											{{else}}
+												{{template "repo/diff/section_unified" dict "file" . "root" $}}
+											{{end}}
+										</table>
 									{{end}}
-								</table>
+								</div>
+								{{if $showFileViewToggle}}
+									<div id="diff-rendered-{{$file.NameHash}}" class="file-body file-code {{if $.IsSplitStyle}} code-diff-split{{else}} code-diff-unified{{end}}">
+										<table class="chroma w-100">
+											{{if $isImage}}
+												{{template "repo/diff/image_diff" dict "file" . "root" $ "blobBase" $blobBase "blobHead" $blobHead}}
+											{{else}}
+												{{template "repo/diff/csv_diff" dict "file" . "root" $ "blobBase" $blobBase "blobHead" $blobHead}}
+											{{end}}
+										</table>
+									</div>
+								{{end}}
 							</div>
-						{{end}}
-					</div>
-				</div>
-			{{end}}
+						</div>
+					{{end}}
 
-			{{if .Diff.IsIncomplete}}
-				<div class="diff-file-box diff-box file-content mt-3" id="diff-incomplete">
-					<h4 class="ui top attached normal header df ac sb">
-						{{$.locale.Tr "repo.diff.too_many_files"}}
-						<a class="ui basic tiny button" id="diff-show-more-files" data-href="{{$.Link}}?skip-to={{.Diff.End}}&file-only=true">{{.locale.Tr "repo.diff.show_more"}}</a>
-					</h4>
+					{{if .Diff.IsIncomplete}}
+						<div class="diff-file-box diff-box file-content mt-3" id="diff-incomplete">
+							<h4 class="ui top attached normal header df ac sb">
+								{{$.locale.Tr "repo.diff.too_many_files"}}
+								<a class="ui basic tiny button" id="diff-show-more-files" data-href="{{$.Link}}?skip-to={{.Diff.End}}&file-only=true">{{.locale.Tr "repo.diff.show_more"}}</a>
+							</h4>
+						</div>
+					{{end}}
 				</div>
-			{{end}}
 		</div>
 
 		{{if not $.Repository.IsArchived}}
diff --git a/templates/repo/diff/compare.tmpl b/templates/repo/diff/compare.tmpl
index 029e7717a4..e0e6837203 100644
--- a/templates/repo/diff/compare.tmpl
+++ b/templates/repo/diff/compare.tmpl
@@ -1,7 +1,7 @@
 {{template "base/head" .}}
 <div class="page-content repository diff {{if .PageIsComparePull}}compare pull{{end}}">
 	{{template "repo/header" .}}
-	<div class="ui container {{if .IsSplitStyle}}fluid padded{{end}}">
+	<div class="ui container fluid padded">
 
 	<h2 class="ui header">
 		{{if and $.PageIsComparePull $.IsSigned (not .Repository.IsArchived)}}
diff --git a/templates/repo/diff/options_dropdown.tmpl b/templates/repo/diff/options_dropdown.tmpl
index 18fa100dcf..2cb5abcb36 100644
--- a/templates/repo/diff/options_dropdown.tmpl
+++ b/templates/repo/diff/options_dropdown.tmpl
@@ -1,7 +1,7 @@
 <div class="ui dropdown tiny basic button icon-button tooltip" data-content="{{.locale.Tr "repo.diff.options_button"}}">
 	{{svg "octicon-kebab-horizontal"}}
 	<div class="menu">
-		<a class="item tiny basic toggle button" data-target="#diff-files">{{.locale.Tr "repo.diff.show_diff_stats"}}</a>
+		<a class="item tiny basic toggle button" id="show-file-list-btn">{{.locale.Tr "repo.diff.show_diff_stats"}}</a>
 		{{if .Issue.Index}}
 			<a class="item" href="{{$.RepoLink}}/pulls/{{.Issue.Index}}.patch" download="{{.Issue.Index}}.patch">{{.locale.Tr "repo.diff.download_patch"}}</a>
 			<a class="item" href="{{$.RepoLink}}/pulls/{{.Issue.Index}}.diff" download="{{.Issue.Index}}.diff">{{.locale.Tr "repo.diff.download_diff"}}</a>
diff --git a/templates/repo/pulls/files.tmpl b/templates/repo/pulls/files.tmpl
index 9b24000002..7b72f7f815 100644
--- a/templates/repo/pulls/files.tmpl
+++ b/templates/repo/pulls/files.tmpl
@@ -5,7 +5,7 @@
 
 <div class="page-content repository view issue pull files diff">
 	{{template "repo/header" .}}
-	<div class="ui container {{if .IsSplitStyle}}fluid padded{{end}}">
+	<div class="ui container fluid padded">
 		<div class="navbar">
 			{{template "repo/issue/navbar" .}}
 			<div class="ui right">
diff --git a/web_src/js/components/DiffFileList.vue b/web_src/js/components/DiffFileList.vue
new file mode 100644
index 0000000000..2a9aa77377
--- /dev/null
+++ b/web_src/js/components/DiffFileList.vue
@@ -0,0 +1,81 @@
+<template>
+  <ol class="diff-detail-box diff-stats m-0" id="diff-files" v-if="fileListIsVisible">
+    <li v-for="file in files" :key="file.NameHash">
+      <div class="bold df ac pull-right">
+        <span v-if="file.IsBin" class="ml-1 mr-3">{{ binaryFileMessage }}</span>
+        {{ file.IsBin ? '' : file.Addition + file.Deletion }}
+        <span v-if="!file.IsBin" class="diff-stats-bar tooltip mx-3" :data-content="statisticsMessage.replace('%d', (file.Addition + file.Deletion)).replace('%d', file.Addition).replace('%d', file.Deletion)">
+          <div class="diff-stats-add-bar" :style="{ 'width': diffStatsWidth(file.Addition, file.Deletion) }" />
+        </span>
+      </div>
+      <!-- todo finish all file status, now modify, add, delete and rename -->
+      <span :class="['status', diffTypeToString(file.Type), 'tooltip']" :data-content="diffTypeToString(file.Type)" data-position="right center">&nbsp;</span>
+      <a class="file mono" :href="'#diff-' + file.NameHash">{{ file.Name }}</a>
+    </li>
+    <li v-if="isIncomplete" id="diff-too-many-files-stats" class="pt-2">
+      <span class="file df ac sb">{{ tooManyFilesMessage }}
+        <a :class="['ui', 'basic', 'tiny', 'button', isLoadingNewData === true ? 'disabled' : '']" id="diff-show-more-files-stats" @click.stop="loadMoreData">{{ showMoreMessage }}</a>
+      </span>
+    </li>
+  </ol>
+</template>
+
+<script>
+import {initTooltip} from '../modules/tippy.js';
+import {doLoadMoreFiles} from '../features/repo-diff.js';
+
+const {pageData} = window.config;
+
+export default {
+  name: 'DiffFileList',
+
+  data: () => {
+    return pageData.diffFileInfo;
+  },
+
+  watch: {
+    fileListIsVisible(newValue) {
+      if (newValue === true) {
+        this.$nextTick(() => {
+          for (const el of this.$el.querySelectorAll('.tooltip')) {
+            initTooltip(el);
+          }
+        });
+      }
+    }
+  },
+
+  mounted() {
+    document.getElementById('show-file-list-btn').addEventListener('click', this.toggleFileList);
+  },
+
+  unmounted() {
+    document.getElementById('show-file-list-btn').removeEventListener('click', this.toggleFileList);
+  },
+
+  methods: {
+    toggleFileList() {
+      this.fileListIsVisible = !this.fileListIsVisible;
+    },
+    diffTypeToString(pType) {
+      const diffTypes = {
+        1: 'add',
+        2: 'modify',
+        3: 'del',
+        4: 'rename',
+        5: 'copy',
+      };
+      return diffTypes[pType];
+    },
+    diffStatsWidth(adds, dels) {
+      return `${adds / (adds + dels) * 100}%`;
+    },
+    loadMoreData() {
+      this.isLoadingNewData = true;
+      doLoadMoreFiles(this.link, this.diffEnd, () => {
+        this.isLoadingNewData = false;
+      });
+    }
+  },
+};
+</script>
diff --git a/web_src/js/components/DiffFileTree.vue b/web_src/js/components/DiffFileTree.vue
new file mode 100644
index 0000000000..d0962254cd
--- /dev/null
+++ b/web_src/js/components/DiffFileTree.vue
@@ -0,0 +1,129 @@
+<template>
+  <div
+    v-show="fileTreeIsVisible"
+    id="diff-file-tree"
+    class="mr-3 mt-3 diff-detail-box"
+  >
+    <!-- only render the tree if we're visible. in many cases this is something that doesn't change very often -->
+    <div class="ui list" v-if="fileTreeIsVisible">
+      <DiffFileTreeItem v-for="item in fileTree" :key="item.name" :item="item" />
+    </div>
+    <div v-if="isIncomplete" id="diff-too-many-files-stats" class="pt-2">
+      <span>{{ tooManyFilesMessage }}</span><a :class="['ui', 'basic', 'tiny', 'button', isLoadingNewData === true ? 'disabled' : '']" id="diff-show-more-files-stats" @click.stop="loadMoreData">{{ showMoreMessage }}</a>
+    </div>
+  </div>
+</template>
+
+<script>
+import DiffFileTreeItem from './DiffFileTreeItem.vue';
+import {doLoadMoreFiles} from '../features/repo-diff.js';
+
+const {pageData} = window.config;
+const LOCAL_STORAGE_KEY = 'diff_file_tree_visible';
+
+export default {
+  name: 'DiffFileTree',
+  components: {DiffFileTreeItem},
+
+  data: () => {
+    const fileTreeIsVisible = localStorage.getItem(LOCAL_STORAGE_KEY) === 'true';
+    pageData.diffFileInfo.fileTreeIsVisible = fileTreeIsVisible;
+    return pageData.diffFileInfo;
+  },
+
+  computed: {
+    fileTree() {
+      const result = [];
+      for (const file of this.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 = {
+            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) => {
+        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);
+      return result;
+    }
+  },
+
+  mounted() {
+    // ensure correct buttons when we are mounted to the dom
+    this.adjustToggleButton(this.fileTreeIsVisible);
+    document.querySelector('.diff-toggle-file-tree-button').addEventListener('click', this.toggleVisibility);
+  },
+  unmounted() {
+    document.querySelector('.diff-toggle-file-tree-button').removeEventListener('click', this.toggleVisibility);
+  },
+  methods: {
+    toggleVisibility() {
+      this.updateVisibility(!this.fileTreeIsVisible);
+    },
+    updateVisibility(visible) {
+      this.fileTreeIsVisible = visible;
+      localStorage.setItem(LOCAL_STORAGE_KEY, this.fileTreeIsVisible);
+      this.adjustToggleButton(this.fileTreeIsVisible);
+    },
+    adjustToggleButton(visible) {
+      const [toShow, toHide] = document.querySelectorAll('.diff-toggle-file-tree-button .icon');
+      toShow.classList.toggle('hide', visible);  // hide the toShow icon if the tree is visible
+      toHide.classList.toggle('hide', !visible); // similarly
+    },
+    loadMoreData() {
+      this.isLoadingNewData = true;
+      doLoadMoreFiles(this.link, this.diffEnd, () => {
+        this.isLoadingNewData = false;
+      });
+    }
+  },
+};
+</script>
diff --git a/web_src/js/components/DiffFileTreeItem.vue b/web_src/js/components/DiffFileTreeItem.vue
new file mode 100644
index 0000000000..4f20f1e66a
--- /dev/null
+++ b/web_src/js/components/DiffFileTreeItem.vue
@@ -0,0 +1,150 @@
+<template>
+  <div v-show="show">
+    <div class="item" :class="item.isFile ? 'filewrapper p-1' : ''">
+      <!-- Files -->
+      <SvgIcon
+        v-if="item.isFile"
+        data-position="right center"
+        name="octicon-file"
+        class="svg-icon file"
+      />
+      <a
+        v-if="item.isFile"
+        class="file ellipsis"
+        :href="item.isFile ? '#diff-' + item.file.NameHash : ''"
+      >{{ item.name }}</a>
+      <SvgIcon
+        v-if="item.isFile"
+        data-position="right center"
+        :name="getIconForDiffType(item.file.Type)"
+        :class="['svg-icon', getIconForDiffType(item.file.Type), 'status']"
+      />
+
+      <!-- Directories -->
+      <div v-if="!item.isFile" class="directory p-1" @click.stop="handleClick(item.isFile)">
+        <SvgIcon
+          class="svg-icon"
+          :name="collapsed ? 'octicon-chevron-right' : 'octicon-chevron-down'"
+        />
+        <SvgIcon
+          class="svg-icon directory"
+          name="octicon-file-directory-fill"
+        />
+        <span class="ellipsis">{{ item.name }}</span>
+      </div>
+      <div v-show="!collapsed">
+        <DiffFileTreeItem v-for="childItem in item.children" :key="childItem.name" :item="childItem" class="list" />
+      </div>
+    </div>
+  </div>
+</template>
+
+<script>
+import {SvgIcon} from '../svg.js';
+
+export default {
+  name: 'DiffFileTreeItem',
+  components: {
+    SvgIcon,
+  },
+
+  props: {
+    item: {
+      type: Object,
+      required: true
+    },
+    show: {
+      type: Boolean,
+      required: false,
+      default: true
+    }
+  },
+
+  data: () => ({
+    collapsed: false,
+  }),
+  methods: {
+    handleClick(itemIsFile) {
+      if (itemIsFile) {
+        return;
+      }
+      this.$set(this, 'collapsed', !this.collapsed);
+    },
+    getIconForDiffType(pType) {
+      const diffTypes = {
+        1: 'octicon-diff-added',
+        2: 'octicon-diff-modified',
+        3: 'octicon-diff-removed',
+        4: 'octicon-diff-renamed',
+        5: 'octicon-diff-modified', // there is no octicon for copied, so modified should be ok
+      };
+      return diffTypes[pType];
+    },
+  },
+};
+</script>
+
+<style scoped>
+span.svg-icon.status {
+  float: right;
+}
+span.svg-icon.file {
+  color: var(--color-secondary-dark-7);
+}
+
+span.svg-icon.directory {
+  color: var(--color-primary);
+}
+
+span.svg-icon.octicon-diff-modified {
+  color: var(--color-yellow);
+}
+
+span.svg-icon.octicon-diff-added {
+  color: var(--color-green);
+}
+
+span.svg-icon.octicon-diff-removed {
+  color: var(--color-red);
+}
+
+span.svg-icon.octicon-diff-renamed {
+  color: var(--color-teal);
+}
+
+.item.filewrapper {
+  display: grid !important;
+  grid-template-columns: 20px 7fr 1fr;
+  padding-left: 18px !important;
+}
+
+.item.filewrapper:hover {
+  color: var(--color-text);
+  background: var(--color-hover);
+  border-radius: 4px;
+}
+
+div.directory {
+  display: grid;
+  grid-template-columns: 18px 20px auto;
+}
+
+div.directory:hover {
+  color: var(--color-text);
+  background: var(--color-hover);
+  border-radius: 4px;
+}
+
+div.list {
+  padding-bottom: 0 !important;
+  padding-top: inherit !important;
+}
+
+a {
+  text-decoration: none;
+}
+
+a:hover {
+  text-decoration: none;
+}
+</style>
diff --git a/web_src/js/features/repo-diff-filetree.js b/web_src/js/features/repo-diff-filetree.js
new file mode 100644
index 0000000000..9eba3cf887
--- /dev/null
+++ b/web_src/js/features/repo-diff-filetree.js
@@ -0,0 +1,21 @@
+import Vue from 'vue';
+import DiffFileTree from '../components/DiffFileTree.vue';
+import DiffFileList from '../components/DiffFileList.vue';
+
+export default function initDiffFileTree() {
+  const el = document.getElementById('diff-file-tree-container');
+  if (!el) return;
+
+  const View = Vue.extend({
+    render: (createElement) => createElement(DiffFileTree),
+  });
+  new View().$mount(el);
+
+  const fileListElement = document.getElementById('diff-file-list-container');
+  if (!fileListElement) return;
+
+  const fileListView = Vue.extend({
+    render: (createElement) => createElement(DiffFileList),
+  });
+  new fileListView().$mount(fileListElement);
+}
diff --git a/web_src/js/features/repo-diff.js b/web_src/js/features/repo-diff.js
index 0a59bcf1c2..0fb7ee22d7 100644
--- a/web_src/js/features/repo-diff.js
+++ b/web_src/js/features/repo-diff.js
@@ -68,7 +68,6 @@ export function initRepoDiffConversationForm() {
     initCompReactionSelector($newConversationHolder);
   });
 
-
   $(document).on('click', '.resolve-conversation', async function (e) {
     e.preventDefault();
     const comment_id = $(this).data('comment-id');
@@ -118,32 +117,27 @@ function onShowMoreFiles() {
   countAndUpdateViewedFiles();
 }
 
-export function initRepoDiffShowMore() {
-  $('#diff-files, #diff-file-boxes').on('click', '#diff-show-more-files, #diff-show-more-files-stats', (e) => {
-    e.preventDefault();
-
-    if ($(e.target).hasClass('disabled')) {
+export function doLoadMoreFiles(link, diffEnd, callback) {
+  const url = `${link}?skip-to=${diffEnd}&file-only=true`;
+  $.ajax({
+    type: 'GET',
+    url,
+  }).done((resp) => {
+    if (!resp) {
+      callback(resp);
       return;
     }
-    $('#diff-show-more-files, #diff-show-more-files-stats').addClass('disabled');
-
-    const url = $('#diff-show-more-files, #diff-show-more-files-stats').data('href');
-    $.ajax({
-      type: 'GET',
-      url,
-    }).done((resp) => {
-      if (!resp) {
-        $('#diff-show-more-files, #diff-show-more-files-stats').removeClass('disabled');
-        return;
-      }
-      $('#diff-too-many-files-stats').remove();
-      $('#diff-files').append($(resp).find('#diff-files li'));
-      $('#diff-incomplete').replaceWith($(resp).find('#diff-file-boxes').children());
-      onShowMoreFiles();
-    }).fail(() => {
-      $('#diff-show-more-files, #diff-show-more-files-stats').removeClass('disabled');
-    });
+    // By simply rerunning the script we add the new data to our existing
+    // pagedata object. this triggers vue and the filetree and filelist will
+    // render the new elements.
+    $('body').append($(resp).find('script#diff-data-script'));
+    callback(resp);
+  }).fail(() => {
+    callback();
   });
+}
+
+export function initRepoDiffShowMore() {
   $(document).on('click', 'a.diff-show-more-button', (e) => {
     e.preventDefault();
     const $target = $(e.target);
@@ -163,7 +157,6 @@ export function initRepoDiffShowMore() {
         $target.removeClass('disabled');
         return;
       }
-
       $target.parent().replaceWith($(resp).find('#diff-file-boxes .diff-file-body .file-body').children());
       onShowMoreFiles();
     }).fail(() => {
diff --git a/web_src/js/index.js b/web_src/js/index.js
index bd56fff773..b13ad0e13a 100644
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@@ -23,6 +23,7 @@ import {initRepoIssueContentHistory} from './features/repo-issue-content.js';
 import {initStopwatch} from './features/stopwatch.js';
 import {initFindFileInRepo} from './features/repo-findfile.js';
 import {initCommentContent, initMarkupContent} from './markup/content.js';
+import initDiffFileTree from './features/repo-diff-filetree.js';
 
 import {initUserAuthLinkAccountView, initUserAuthOauth2} from './features/user-auth.js';
 import {
@@ -158,6 +159,7 @@ $(document).ready(() => {
   initRepoDiffFileViewToggle();
   initRepoDiffReviewButton();
   initRepoDiffShowMore();
+  initDiffFileTree();
   initRepoEditor();
   initRepoGraphGit();
   initRepoIssueContentHistory();
diff --git a/web_src/js/svg.js b/web_src/js/svg.js
index 9c39852c30..6677bf83cb 100644
--- a/web_src/js/svg.js
+++ b/web_src/js/svg.js
@@ -2,6 +2,11 @@ import octiconChevronDown from '../../public/img/svg/octicon-chevron-down.svg';
 import octiconChevronRight from '../../public/img/svg/octicon-chevron-right.svg';
 import octiconCopy from '../../public/img/svg/octicon-copy.svg';
 import octiconClock from '../../public/img/svg/octicon-clock.svg';
+import octiconDiffAdded from '../../public/img/svg/octicon-diff-added.svg';
+import octiconDiffModified from '../../public/img/svg/octicon-diff-modified.svg';
+import octiconDiffRemoved from '../../public/img/svg/octicon-diff-removed.svg';
+import octiconDiffRenamed from '../../public/img/svg/octicon-diff-renamed.svg';
+import octiconFileDirectoryFill from '../../public/img/svg/octicon-file-directory-fill.svg';
 import octiconGitMerge from '../../public/img/svg/octicon-git-merge.svg';
 import octiconGitPullRequest from '../../public/img/svg/octicon-git-pull-request.svg';
 import octiconIssueClosed from '../../public/img/svg/octicon-issue-closed.svg';
@@ -17,6 +22,9 @@ import octiconRepoForked from '../../public/img/svg/octicon-repo-forked.svg';
 import octiconRepoTemplate from '../../public/img/svg/octicon-repo-template.svg';
 import octiconTriangleDown from '../../public/img/svg/octicon-triangle-down.svg';
 import octiconFile from '../../public/img/svg/octicon-file.svg';
+import octiconSidebarExpand from '../../public/img/svg/octicon-sidebar-expand.svg';
+import octiconSidebarCollapse from '../../public/img/svg/octicon-sidebar-collapse.svg';
+
 
 import Vue from 'vue';
 
@@ -40,8 +48,16 @@ export const svgs = {
   'octicon-repo-template': octiconRepoTemplate,
   'octicon-triangle-down': octiconTriangleDown,
   'octicon-file': octiconFile,
+  'octicon-file-directory-fill': octiconFileDirectoryFill,
+  'octicon-sidebar-expand': octiconSidebarExpand,
+  'octicon-sidebar-collapse': octiconSidebarCollapse,
+  'octicon-diff-added': octiconDiffAdded,
+  'octicon-diff-modified': octiconDiffModified,
+  'octicon-diff-removed': octiconDiffRemoved,
+  'octicon-diff-renamed': octiconDiffRenamed,
 };
 
+
 const parser = new DOMParser();
 const serializer = new XMLSerializer();
 
diff --git a/web_src/less/_repository.less b/web_src/less/_repository.less
index 44e9a0430e..f30bafa4cc 100644
--- a/web_src/less/_repository.less
+++ b/web_src/less/_repository.less
@@ -3068,6 +3068,35 @@ td.blob-excerpt {
   padding-left: 8px;
 }
 
+#diff-container {
+  display: flex;
+}
+#diff-file-boxes {
+  flex: 1;
+}
+
+#diff-file-tree {
+  width: 20%;
+  max-width: 380px;
+  line-height: inherit;
+  position: sticky;
+  padding-top: 0;
+  top: 47px;
+  max-height: calc(100vh - 50px);
+  height: 100%;
+  overflow-y: auto;
+}
+
+@media @mediaMdAndDown {
+  #diff-file-tree {
+    display: none;
+  }
+
+  .diff-toggle-file-tree-button {
+    display: none;
+  }
+}
+
 .ui.message.unicode-escape-prompt {
   margin-bottom: 0;
   border-radius: 0;