Disable password autocomplete in mirror form fill

Chrome and other browsers ignore autocomplete=false and autocomplete=off
now. This causes the mirroring section to expand whenever a user clicked
"Expand" in the Repository settings.

https://developers.google.com/web/fundamentals/design-and-ux/input/forms/?hl=en
recommends using new-password as the new field to prevent automatic
filling.

It looks like we already do this in app/views/shared/_field.html.haml.

This is a CE backport of
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8477.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/50812

app/views/projects/mirrors/_authentication_method.html.haml

@@ -15,7 +15,7 @@
     .changing-auth-method= icon('spinner spin lg')
   .well-password-auth.collapse.js-well-password-auth
     = f.label :password, _("Password"), class: "label-bold"
-    = f.password_field :password, value: mirror.password, class: 'form-control'
+    = f.password_field :password, value: mirror.password, class: 'form-control', autocomplete: 'new-password'
   - unless is_push
     .well-ssh-auth.collapse.js-well-ssh-auth
       %p.js-ssh-public-key-present{ class: ('collapse' unless ssh_public_key_present) }

changelogs/unreleased/sh-disable-autocomplete-mirror-settings.yml

+---
+title: Disable password autocomplete in mirror form fill
+merge_request: 23402
+author:
+type: fixed