Hide RSS icon when viewing a file not under a branch (#36135)

Fix #35855

Co-authored-by: Giteabot <[email protected]>

Author: lunny

templates/repo/view_file.tmpl

@@ -62,7 +62,7 @@
 					{{if not .IsDisplayingSource}}data-raw-file-link="{{$.RawFileLink}}"{{end}}
 					data-tooltip-content="{{if .CanCopyContent}}{{ctx.Locale.Tr "copy_content"}}{{else}}{{ctx.Locale.Tr "copy_type_unsupported"}}{{end}}"
 				>{{svg "octicon-copy"}}</a>
-				{{if .EnableFeed}}
+				{{if and .EnableFeed .RefFullName.IsBranch}}
 				<a class="btn-octicon" href="{{$.RepoLink}}/rss/{{$.RefTypeNameSubURL}}/{{PathEscapeSegments .TreePath}}" data-tooltip-content="{{ctx.Locale.Tr "rss_feed"}}">
 					{{svg "octicon-rss"}}
 				</a>