Allow setting custom gitlab config for Gitaly

Administrators may now set `gitlab` configuration values
directly rather than rely on automatic calculations from
the rails service.

Related https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/24530

Changelog: added

Author: Ahmad Sherif

files/gitlab-config-template/gitlab.rb.template

@@ -2589,6 +2589,10 @@ external_url 'GENERATED_EXTERNAL_URL'
 #       { key: 'http.http://example.com.proxy', value: 'http://example.proxy.com' },
 #     ],
 #   },
+#   gitlab: {
+#     url: 'http://localhost:9999',
+#     relative_url_root: '/gitlab-ee',
+#   },
 #   hooks: {
 #     custom_hooks_dir: '/var/opt/gitlab/gitaly/custom_hooks',
 #   },

files/gitlab-cookbooks/gitaly/recipes/enable.rb

@@ -103,7 +103,7 @@
             url: gitlab_url,
             relative_url_root: gitlab_relative_path,
             'http-settings': node.dig('gitlab', 'gitlab_shell', 'http_settings')
-          }.compact,
+          }.merge(node.dig('gitaly', 'configuration', 'gitlab') || {}).compact,
 
           # These options below were historically hard coded values in the template. They
           # are set here to retain the behavior of them not being overridable by the user.

spec/chef/cookbooks/gitaly/recipes/gitaly_spec.rb

@@ -1005,6 +1005,26 @@
     end
   end
 
+  context 'with custom gitlab values' do
+    before do
+      stub_gitlab_rb(
+        gitaly: {
+          configuration: {
+            gitlab: {
+              url: 'http://localhost:9999',
+              relative_url_root: '/gitlab-ee'
+            }
+          }
+        }
+      )
+    end
+
+    it 'creates config file with the custom gitlab values set' do
+      expect(chef_run).to render_file(config_path)
+        .with_content(%r{\[gitlab\]\s+url = "http://localhost:9999"\s+relative_url_root = "/gitlab-ee"})
+    end
+  end
+
   include_examples "consul service discovery", "gitaly", "gitaly"
 end