Add btn-icon class for icon only buttons in issues header

app/views/projects/issues/import_csv/_button.html.haml

@@ -2,7 +2,7 @@
 - can_edit = can?(current_user, :admin_project, @project)
 
 .dropdown.btn-group
-  %button.btn.gl-button.btn-default.rounded-right.text-center{ class: ('has-tooltip' if type == :icon), title: (_('Import issues') if type == :icon),
+  %button.btn.gl-button.rounded-right.btn-default.btn-icon.text-center{ class: ('has-tooltip' if type == :icon), title: (_('Import issues') if type == :icon),
     data: { toggle: 'dropdown', qa_selector: 'import_issues_button' }, 'aria-label' => _('Import issues'), 'aria-haspopup' => 'true', 'aria-expanded' => 'false' }
     - if type == :icon
       = sprite_icon('import')

app/views/shared/issuable/_feed_buttons.html.haml

-= link_to safe_params.merge(rss_url_options), class: 'btn gl-button btn-default has-tooltip', data: { container: 'body', testid: 'rss-feed-link' }, title: _('Subscribe to RSS feed') do
+= link_to safe_params.merge(rss_url_options), class: 'btn gl-button btn-default btn-icon has-tooltip', data: { container: 'body', testid: 'rss-feed-link' }, title: _('Subscribe to RSS feed') do
   = sprite_icon('rss', css_class: 'qa-rss-icon')
-= link_to safe_params.merge(calendar_url_options), class: 'btn gl-button btn-default has-tooltip', data: { container: 'body' }, title: _('Subscribe to calendar') do
+= link_to safe_params.merge(calendar_url_options), class: 'btn gl-button btn-default btn-icon has-tooltip', data: { container: 'body' }, title: _('Subscribe to calendar') do
   = sprite_icon('calendar')

app/views/shared/issuable/csv_export/_button.html.haml

 - if current_user
-  %button.csv_download_link.btn.gl-button.btn-default.has-tooltip{ title: _('Export as CSV'),
+  %button.csv_download_link.btn.gl-button.btn-default.btn-icon.has-tooltip{ title: _('Export as CSV'),
     data: { toggle: 'modal', target: ".#{issuable_type}-export-modal", qa_selector: 'export_as_csv_button' } }
     = sprite_icon('export')

changelogs/unreleased/btn-icon-issues.yml

+---
+title: Add btn-icon class for icon only buttons in issues header
+merge_request: 53562
+author: Yogi (@yo)
+type: other