schacon/ruby-git — pull request #180 by francisluong (2014-09-26 21:12:12+00:00)
Title: Git::Diff - don't convert to empty string if from/to is nil

I was having trouble just getting the code to do a git diff without specifying commits.

```
I, [2014-09-26T16:21:18.444662 #65864] INFO -- : git diff '-p' 'HEAD' '' 2>&1
D, [2014-09-26T16:21:18.444727 #65864] DEBUG -- : fatal: ambiguous argument '': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git [...] -- [...]'
/Users/fluong/.rvm/gems/ruby-2.0.0-p353/gems/git-1.2.8/lib/git/lib.rb:764:in `command': git diff '-p' 'HEAD' '' 2>&1:fatal: ambiguous argument '': unknown revision or path not in the working tree. (Git::GitExecuteError)
Use '--' to separate paths from revisions, like this:
'git [...] -- [...]'
from /Users/fluong/.rvm/gems/ruby-2.0.0-p353/gems/git-1.2.8/lib/git/lib.rb:276:in `diff_full'
from /Users/fluong/.rvm/gems/ruby-2.0.0-p353/gems/git-1.2.8/lib/git/diff.rb:100:in `cache_full'
from /Users/fluong/.rvm/gems/ruby-2.0.0-p353/gems/git-1.2.8/lib/git/diff.rb:51:in `patch'
from ./git-diff.rb:9:in `

'
```

I think this will fix it.