applyPatch can't handle clearing the file

[chaaz]

If a patch is supposed to completely erase a file, applyPatch will instead keep the first line.

$ cat testfile 
This
is
a
file,
yo
$ cat > testfile          # empty the file out
$ cat testfile
$ git diff > diff.patch   # create unified patch w/ git
$ cat diff.patch 
diff --git a/testfile b/testfile
index c9d61c6..e69de29 100644
--- a/testfile
+++ b/testfile
@@ -1,5 +0,0 @@
-This
-is
-a
-file,
-yo
$ git checkout -- .       # restore testfile
$ cat testfile 
This
is
a
file,
yo
$ patch -p1 < diff.patch  # test with 'patch'
patching file testfile
$ cat testfile            # yep, worked
$ git checkout -- .       # restore testfile again
$ cat patch.js
var fs = require('fs');
var diff = require('diff');

console.log(
  diff.applyPatch(
    fs.readFileSync('testfile', 'utf8'),
    fs.readFileSync('diff.patch', 'utf8')
  )
);

$ node patch.js           # this should be empty
This