Define constants only if not defined yet and freeze them

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/models/commit.rb

@@ -12,11 +12,11 @@ class Commit
 
   attr_accessor :project
 
-  DIFF_SAFE_LINES = Gitlab::Git::DiffCollection::DEFAULT_LIMITS[:max_lines]
+  DIFF_SAFE_LINES ||= Gitlab::Git::DiffCollection::DEFAULT_LIMITS[:max_lines]
 
   # Commits above this size will not be rendered in HTML
-  DIFF_HARD_LIMIT_FILES = 1000 unless defined?(DIFF_HARD_LIMIT_FILES)
-  DIFF_HARD_LIMIT_LINES = 50000 unless defined?(DIFF_HARD_LIMIT_LINES)
+  DIFF_HARD_LIMIT_FILES ||= 1000
+  DIFF_HARD_LIMIT_LINES ||= 50000
 
   class << self
     def decorate(commits, project)

lib/file_size_validator.rb

 class FileSizeValidator < ActiveModel::EachValidator
-  MESSAGES  = { is: :wrong_size, minimum: :size_too_small, maximum: :size_too_big }.freeze
-  CHECKS    = { is: :==, minimum: :>=, maximum: :<= }.freeze
+  MESSAGES ||= { is: :wrong_size, minimum: :size_too_small, maximum: :size_too_big }.freeze
+  CHECKS   ||= { is: :==, minimum: :>=, maximum: :<= }.freeze
 
-  DEFAULT_TOKENIZER = lambda { |value| value.split(//) }
-  RESERVED_OPTIONS  = [:minimum, :maximum, :within, :is, :tokenizer, :too_short, :too_long]
+  DEFAULT_TOKENIZER ||= -> (value) { value.split(//) }.freeze
+  RESERVED_OPTIONS  ||= [:minimum, :maximum, :within, :is, :tokenizer, :too_short, :too_long].freeze
 
   def initialize(options)
     if range = (options.delete(:in) || options.delete(:within))