Add friendly message for unconfirmed users

changelogs/unreleased/show-email-unconfirmed-message-in-git-auth.yml

+---
+title: Provide better git error message when the user is unconfirmed
+merge_request: 37944
+author:
+type: fixed

lib/gitlab/auth/user_access_denied_reason.rb

@@ -17,6 +17,10 @@ module Gitlab
         when :deactivated
           "Your account has been deactivated by your administrator. "\
           "Please log back in from a web browser to reactivate your account at #{Gitlab.config.gitlab.url}"
+        when :unconfirmed
+          "Your primary email address is not confirmed. "\
+          "Please check your inbox for the confirmation instructions. "\
+          "In case the link is expired, you can request a new confirmation email at #{Rails.application.routes.url_helpers.new_user_confirmation_url}"
         else
           "Your account has been blocked."
         end
@@ -31,6 +35,8 @@ module Gitlab
           :terms_not_accepted
         elsif @user.deactivated?
           :deactivated
+        elsif !@user.confirmed?
+          :unconfirmed
         else
           :blocked
         end

spec/lib/gitlab/auth/user_access_denied_reason_spec.rb

@@ -41,5 +41,13 @@ RSpec.describe Gitlab::Auth::UserAccessDeniedReason do
 
       it { is_expected.to eq "Your account has been deactivated by your administrator. Please log back in from a web browser to reactivate your account at #{Gitlab.config.gitlab.url}" }
     end
+
+    context 'when the user is unconfirmed' do
+      before do
+        user.update!(confirmed_at: nil)
+      end
+
+      it { is_expected.to match /Your primary email address is not confirmed/ }
+    end
   end
 end