Make single diff patch limit configurable

- Creates a new column to hold the single patch limit value on
application_settings
- Allows updating this value through the application_settings API
- Calculates single diff patch collapsing limit based on
diff_max_patch_bytes column
- Updates diff limit documentation
- Adds documentation (with warning) as of how one can update this limit

4 files changed, 37 insertions, 2 deletions

diff --git a/app/helpers/application_settings_helper.rb b/app/helpers/application_settings_helper.rb
index c9a5431d18e..15cbfeea609 100644
--- a/app/helpers/application_settings_helper.rb
+++ b/app/helpers/application_settings_helper.rb
@@ -254,7 +254,8 @@ module ApplicationSettingsHelper
       :user_default_internal_regex,
       :user_oauth_applications,
       :version_check_enabled,
-      :web_ide_clientside_preview_enabled
+      :web_ide_clientside_preview_enabled,
+      :diff_max_patch_bytes
     ]
   end
 
diff --git a/app/models/application_setting.rb b/app/models/application_setting.rb
index 5f835a8da75..65a2f760f93 100644
--- a/app/models/application_setting.rb
+++ b/app/models/application_setting.rb
@@ -182,6 +182,12 @@ class ApplicationSetting < ActiveRecord::Base
             numericality: { less_than_or_equal_to: :gitaly_timeout_default },
             if: :gitaly_timeout_default
 
+  validates :diff_max_patch_bytes,
+            presence: true,
+            numericality: { only_integer: true,
+                            greater_than_or_equal_to: Gitlab::Git::Diff::DEFAULT_MAX_PATCH_BYTES,
+                            less_than_or_equal_to: Gitlab::Git::Diff::MAX_PATCH_BYTES_UPPER_BOUND }
+
   validates :user_default_internal_regex, js_regex: true, allow_nil: true
 
   SUPPORTED_KEY_TYPES.each do |type|
@@ -293,7 +299,8 @@ class ApplicationSetting < ActiveRecord::Base
       user_default_external: false,
       user_default_internal_regex: nil,
       user_show_add_ssh_key_message: true,
-      usage_stats_set_by_user_id: nil
+      usage_stats_set_by_user_id: nil,
+      diff_max_patch_bytes: Gitlab::Git::Diff::DEFAULT_MAX_PATCH_BYTES
     }
   end
 
diff --git a/app/views/admin/application_settings/_diff_limits.html.haml b/app/views/admin/application_settings/_diff_limits.html.haml
new file mode 100644
index 00000000000..408e569fe07
--- /dev/null
+++ b/app/views/admin/application_settings/_diff_limits.html.haml
@@ -0,0 +1,16 @@
+= form_for @application_setting, url: admin_application_settings_path(anchor: 'js-merge-request-settings'), html: { class: 'fieldset-form' } do |f|
+  = form_errors(@application_setting)
+
+  %fieldset
+    .form-group
+      = f.label :diff_max_patch_bytes, 'Maximum diff patch size (Bytes)', class: 'label-light'
+      = f.number_field :diff_max_patch_bytes, class: 'form-control'
+      %span.form-text.text-muted
+        Diff files surpassing this limit will be presented as 'too large'
+        and won't be expandable.
+
+        = link_to icon('question-circle'),
+          help_page_path('user/admin_area/diff_limits',
+          anchor: 'maximum-diff-patch-size')
+
+  = f.submit _('Save changes'), class: 'btn btn-success'
diff --git a/app/views/admin/application_settings/show.html.haml b/app/views/admin/application_settings/show.html.haml
index e2043183a97..761555c4189 100644
--- a/app/views/admin/application_settings/show.html.haml
+++ b/app/views/admin/application_settings/show.html.haml
@@ -24,6 +24,17 @@
   .settings-content
     = render 'account_and_limit'
 
+%section.settings.as-diff-limits.no-animate#js-merge-request-settings{ class: ('expanded' if expanded_by_default?) }
+  .settings-header
+    %h4
+      = _('Diff limits')
+    %button.btn.js-settings-toggle{ type: 'button' }
+      = expanded_by_default? ? _('Collapse') : _('Expand')
+    %p
+      = _('Diff content limits')
+  .settings-content
+    = render 'diff_limits'
+
 %section.settings.as-signup.no-animate#js-signup-settings{ class: ('expanded' if expanded_by_default?) }
   .settings-header
     %h4