Redmine

I'm attaching a patch (against r1747) that fixes my #1794 defect issue.

• app/models/repository/darcs.rb
  Before calling the darcs scm adapter, darcs needs the revision number being translated to the scmid. This was working for the entries(), diff() and fetch_changesets() methods. I added this for entry() and cat() in a similar fashion.
• lib/redmine/scm/adapters/darcs_adapter.rb
  Starting from version 2.0.0, darcs supports listing the contents of a file in the repository. I added the code to read the version number and the cat() method (similar to what is there for subversion).

These were my first ruby lines - I hope I didn't screw up ... I'd be happy to see them upstream. Thanks for the great application!