Hide collapse icon in diff with no lines (#21094)

Sometimes (e.g. renaming a file) nothing of the content is changed. In
this case, it makes no sense to show the collapse icon in a diff.

templates/repo/diff/box.tmpl

@@ -79,6 +79,7 @@
 						<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">
+									{{if or (gt $file.Addition 0) (gt $file.Deletion 0) $file.IsBin}}
 										<a role="button" class="fold-file muted mr-2">
 											{{if $file.ShouldBeHidden}}
 												{{svg "octicon-chevron-right" 18}}
@@ -86,6 +87,7 @@
 												{{svg "octicon-chevron-down" 18}}
 											{{end}}
 										</a>
+									{{end}}
 									<div class="bold df ac">
 										{{if $file.IsBin}}
 											<span class="ml-1 mr-3">