Can't get command line diff/merge working

I've tried off and on to get this working, every time with no success.  Finally decided I should ask here instead of giving up :-)

I'm using IntelliJ Community Edition 12.0.  I'm going based off of these docs: http://www.jetbrains.com/idea/webhelp/running-intellij-idea-as-a-diff-or-merge-command-line-tool.html

Here's what I've tried:

1) Run from bin directory:

1. Run "cmd"
2. cd "C:\Program Files (x86)\IntelliJ IDEA Community Edition 12.0\bin"
3. idea.exe diff <abs path to file1> <abc path to file 2>

Result: nothing happens -- no window opens and nothing appears on the command line

2) Run from directory the files are in:

1. Run "cmd"
2. cd <source code folder>
3. "C:\Program Files (x86)\IntelliJ IDEA Community Edition 12.0\bin\idea.exe" diff <filename1> <filename2>

Result: nothing happens

3) Run from directory the files are in, after adding to path:

1. Run "cmd"
2. set PATH=%PATH%;"C:\Program Files (x86)\IntelliJ IDEA Community Edition 12.0\bin"
3. cd <source code folder>
4. idea.exe diff <filename1> <filename2>

Result: nothing happens

4) Run without filenames (which some docs imply is supposed to show usage)

1. Run "cmd"
2. "C:\Program Files (x86)\IntelliJ IDEA Community Edition 12.0\bin\idea.exe" diff

Result: nothing happens

Am I missing something?  The docs make this sound pretty straightforward, and it is definitely supposed to work in this version.

Thanks in advance for your help!

- Peter