So you have a rails app and you need to remove all references to a particular resource (model, controller, views, tests etc.) from Git on the command line in one nice simple command?
git commit *resourcename* -m "deleting all references to resourcename"
[master 29bf6e1] deleting all references to resourcename
9 files changed, 0 insertions(+), 161 deletions(-)
delete mode 100644 app/controllers/resourcenames_controller.rb
delete mode 100644 app/helpers/resourcenames_helper.rb
delete mode 100644 app/models/resourcename.rb
delete mode 100644 app/views/resourcenames/new.html.erb
delete mode 100644 app/views/resourcenames/show.html.erb
delete mode 100644 test/fixtures/resourcenames.yml
delete mode 100644 test/functional/resourcenames_controller_test.rb
delete mode 100644 test/unit/helpers/resourcenames_helper_test.rb
delete mode 100644 test/unit/resourcename_test.rb
(where resroucename is the name of your resource obviously)