Merge branch 'fix-mysql-migration-with-tags' into 'master'

Change the MySQL collation type to utf8_bin to ensure case-sensitive tags are supported

MySQL tables had a collation type of utf8_ci, which makes the name case-insensitive. Previously this migration was run only after indices were built, but it needs to happen before if there is existing data that is case-sensitive. This is an idempotent change, so applying it again in the existing migration (20150425164651) should not change anything.

This is related to !623, but this migration should run before that one.

* Closes #1589
* Closes https://github.com/gitlabhq/gitlabhq/issues/9255

See merge request !625

db/migrate/20150425164646_gitlab_change_collation_for_tag_names.acts_as_taggable_on_engine.rb

+# This migration is a duplicate of 20150425164651_change_collation_for_tag_names.acts_as_taggable_on_engine.rb
+# It shold be applied before the index additions to ensure that `name` is case sensitive.
+
+class GitlabChangeCollationForTagNames < ActiveRecord::Migration
+  def up
+    if ActsAsTaggableOn::Utils.using_mysql?
+      execute("ALTER TABLE tags MODIFY name varchar(255) CHARACTER SET utf8 COLLATE utf8_bin;")
+    end
+  end
+end