Remove asset_sync gem and related code

Reverting https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15734 .
We are not using asset sync currently.

Gemfile

@@ -429,6 +429,3 @@ gem 'flipper-active_support_cache_store', '~> 0.13.0'
 # Structured logging
 gem 'lograge', '~> 0.5'
 gem 'grape_logging', '~> 1.7'
-
-# Asset synchronization
-gem 'asset_sync', '~> 2.4'

Gemfile.lock

@@ -58,11 +58,6 @@ GEM
     asciidoctor (1.5.6.2)
     asciidoctor-plantuml (0.0.8)
       asciidoctor (~> 1.5)
-    asset_sync (2.4.0)
-      activemodel (>= 4.1.0)
-      fog-core
-      mime-types (>= 2.99)
-      unf
     ast (2.4.0)
     atomic (1.1.99)
     attr_encrypted (3.1.0)
@@ -936,7 +931,6 @@ DEPENDENCIES
   asana (~> 0.6.0)
   asciidoctor (~> 1.5.6)
   asciidoctor-plantuml (= 0.0.8)
-  asset_sync (~> 2.4)
   attr_encrypted (~> 3.1.0)
   awesome_print
   babosa (~> 1.0.2)

Gemfile.rails5.lock

@@ -61,11 +61,6 @@ GEM
     asciidoctor (1.5.6.2)
     asciidoctor-plantuml (0.0.8)
       asciidoctor (~> 1.5)
-    asset_sync (2.4.0)
-      activemodel (>= 4.1.0)
-      fog-core
-      mime-types (>= 2.99)
-      unf
     ast (2.4.0)
     atomic (1.1.99)
     attr_encrypted (3.1.0)
@@ -945,7 +940,6 @@ DEPENDENCIES
   asana (~> 0.6.0)
   asciidoctor (~> 1.5.6)
   asciidoctor-plantuml (= 0.0.8)
-  asset_sync (~> 2.4)
   attr_encrypted (~> 3.1.0)
   awesome_print
   babosa (~> 1.0.2)

changelogs/unreleased/remove-asset-sync.yml

+---
+title: Remove asset_sync gem from Gemfile and related code from codebase
+merge_request: 22610
+author:
+type: other

config/initializers/asset_sync.rb

-AssetSync.configure do |config|
-  # Disable the asset_sync gem by default. If it is enabled, but not configured,
-  # asset_sync will cause the build to fail.
-  config.enabled =  if ENV.has_key?('ASSET_SYNC_ENABLED')
-                      ENV['ASSET_SYNC_ENABLED'] == 'true'
-                    else
-                      false
-                    end
-
-  # Pulled from https://github.com/AssetSync/asset_sync/blob/v2.2.0/lib/asset_sync/engine.rb#L15-L40
-  # This allows us to disable asset_sync by default and configure through environment variables
-  # Updates to asset_sync gem should be checked
-  config.fog_provider = ENV['FOG_PROVIDER'] if ENV.has_key?('FOG_PROVIDER')
-  config.fog_directory = ENV['FOG_DIRECTORY'] if ENV.has_key?('FOG_DIRECTORY')
-  config.fog_region = ENV['FOG_REGION'] if ENV.has_key?('FOG_REGION')
-
-  config.aws_access_key_id = ENV['ASSETS_AWS_ACCESS_KEY_ID'] if ENV.has_key?('ASSETS_AWS_ACCESS_KEY_ID')
-  config.aws_secret_access_key = ENV['ASSETS_AWS_SECRET_ACCESS_KEY'] if ENV.has_key?('ASSETS_AWS_SECRET_ACCESS_KEY')
-  config.aws_reduced_redundancy = ENV['AWS_REDUCED_REDUNDANCY'] == true  if ENV.has_key?('AWS_REDUCED_REDUNDANCY')
-
-  config.rackspace_username = ENV['RACKSPACE_USERNAME'] if ENV.has_key?('RACKSPACE_USERNAME')
-  config.rackspace_api_key = ENV['RACKSPACE_API_KEY'] if ENV.has_key?('RACKSPACE_API_KEY')
-
-  config.google_storage_access_key_id = ENV['GOOGLE_STORAGE_ACCESS_KEY_ID'] if ENV.has_key?('GOOGLE_STORAGE_ACCESS_KEY_ID')
-  config.google_storage_secret_access_key = ENV['GOOGLE_STORAGE_SECRET_ACCESS_KEY'] if ENV.has_key?('GOOGLE_STORAGE_SECRET_ACCESS_KEY')
-
-  config.existing_remote_files = ENV['ASSET_SYNC_EXISTING_REMOTE_FILES'] || "keep"
-
-  config.gzip_compression = (ENV['ASSET_SYNC_GZIP_COMPRESSION'] == 'true') if ENV.has_key?('ASSET_SYNC_GZIP_COMPRESSION')
-  config.manifest = (ENV['ASSET_SYNC_MANIFEST'] == 'true') if ENV.has_key?('ASSET_SYNC_MANIFEST')
-end