scm: use to_s for revision in find_changeset_by_name method
On Rails 3.0.11, Subversion functional test fails.
<pre> Error: test_directory_diff(RepositoriesSubversionControllerTest) NoMethodError: undefined method `match' for 2:Fixnum app/models/repository.rb:234:in `find_changeset_by_name' </pre>
Authored by: tmaruyama 2012-02-23
Parent: [r8930]
Child: [r8932]
