ActiveRecord::Migration#copy allows to copy migrations from one place
to another, changing migrations versions and adding scope to filename.

For example:
ActiveRecord::Migration.copy("db/migrate",
        :blog_engine => "vendor/gems/blog/db/migrate")

will copy all migrations from vendor/gems/blog/db/migrate to db/migrate
with such format:

Versions of copied migrations will be reversioned to be appended after
migrations that already exists in db/migrate

Add support for interleaving migrations by storing which migrations have run in the new schema_migrations table. Closes #11493 [jordi]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@9244 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8658 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@818 5ecf4fe2-1ee6-0310-87b1-e25e094e27de