Fix squash doc links

* 'Learn more' should be 'about this feature'
* The feature is to squash and merge at once, not squash before merge

app/views/projects/merge_requests/widget/open/_accept.html.haml

@@ -43,7 +43,7 @@
           = hidden_field_tag :squash, '0', id: nil
           = check_box_tag :squash, '1', @merge_request.squash
           Squash commits
-          = link_to icon('question-circle'), help_page_path('user/project/merge_requests/squash_before_merge'), title: 'Learn more', data: {toggle: 'tooltip', placement: 'bottom', container: 'body'}
+          = link_to icon('question-circle'), help_page_path('user/project/merge_requests/squash_and_merge'), title: 'About this feature', data: {toggle: 'tooltip', placement: 'bottom', container: 'body'}
 
       .accept-control
         - if @project.merge_requests_ff_only_enabled

app/views/shared/issuable/form/_merge_params.html.haml

@@ -17,4 +17,4 @@
         = hidden_field_tag 'merge_request[squash]', '0', id: nil
         = check_box_tag 'merge_request[squash]', '1', issuable.squash
         Squash commits when merge request is accepted.
-        = link_to 'Learn more', help_page_path('user/project/merge_requests/squash_before_merge')
+        = link_to 'About this feature', help_page_path('user/project/merge_requests/squash_and_merge')

doc/user/project/merge_requests/squash_before_merge.md → doc/user/project/merge_requests/squash_and_merge.md

-# Squash before merge
+# Squash and merge
 
 Documentation forthcoming.