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

2 files changed, 27 insertions, 1 deletions

diff --git a/db/migrate/20180924141949_add_diff_max_patch_bytes_to_application_settings.rb b/db/migrate/20180924141949_add_diff_max_patch_bytes_to_application_settings.rb
new file mode 100644
index 00000000000..084dfc65ce5
--- /dev/null
+++ b/db/migrate/20180924141949_add_diff_max_patch_bytes_to_application_settings.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddDiffMaxPatchBytesToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:application_settings,
+                            :diff_max_patch_bytes,
+                            :integer,
+                            default: 100.kilobytes,
+                            allow_null: false)
+  end
+
+  def down
+    remove_column(:application_settings, :diff_max_patch_bytes)
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f92d8005dfb..2e0152af81d 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180917172041) do
+ActiveRecord::Schema.define(version: 20180924141949) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -171,6 +171,7 @@ ActiveRecord::Schema.define(version: 20180917172041) do
     t.boolean "user_show_add_ssh_key_message", default: true, null: false
     t.integer "usage_stats_set_by_user_id"
     t.integer "receive_max_input_size"
+    t.integer "diff_max_patch_bytes", default: 102400, null: false
   end
 
   create_table "audit_events", force: :cascade do |t|