This week Google added a CodeMirror-powered code editor to Google Project Hosting. This enables developers to make quick changes to Google projects from within the browser without having to deal with Mercurial or Subversion.
It previews the changes that you are about to commit and, for contributors without commit privileges, it can file changes as a patch in the project’s issue tracker.
What do you think? Will this be useful? Should GitHub and other code hosts implement something like this?