Please add screenshots to your review request.

I'd prefer if you could make another function that wraps diff_line and use it in the map() above. This way we only have to iterate through the lines once instead of twice.

Can you rename this "opcodes_with_metadata"?

The grammar in this comment is wrong. "this whole thing"?

You're iterating over this thing 3 times.

Add spaces between parameters:

for i, j in zip(xrange(i1, i2), xrange(j1, j2)):

Missing space before the second "differ"

And here's a 4th iteration, but this one is a generator. If you can fold all of these loops in together and keep the yield, it'll make it all much more efficient.

The way you're using this "num_whitespace_chunks" variable is very odd. It seems to be a negative count of non-whitespace chunks, from my reading.

Here's how I'd write it:

file['whitespace_only'] = True
for j, chunk in enumerate(file['chunks']):
    chunk['index'] = j
    if chunk['change'] != 'equal':
        file['changed_chunks'].append(chunk)
        if not chunk['meta'].get('whitespace_chunk', False):
            file['whitespace_only'] = False

These should only be indented 4 spaces.

Add an extra blank line here.

This style should be in the .css file for the class.

hi hello

Better give acomment

This doesn't really describe the function. Might be better as a comment.

Also, "Access"

Trailing whitespace.

I don't know that the comment is really necessary.

"WS" -> "whitespace"

Space after the :

Also, on the comments, there should be a space after #, and the comment should end with a period.

Space between i, j

Space on both sides of +

Please add a documentation comment above this describing the function.

Since we reference table.sidebyside instances many times, we should store the result of $("table.sidebyside") in a variable and reference that variable for all other uses.

Can you put comments on their own lines? With a blank line preceding them.

Blank line before this.

Two blank lines here.

Rather than having onclick, I'd prefer that diffviewer.js register these actions for these links. You can give them IDs to reference them.

This is looking awesome. A few more things I noticed and then I think it'll be ready to commit! :)

"accesses"

Contents of the dictionary should be indented 4 spaces from the return statement.

Since we only ever define this data in one spot, just do it inline here.

Since we only ever append the group in one place, we can instead yield directly here, which will prevent one more loop, improving efficiency.

Trailing whitespace.

This should move outside the for loop, so we avoid compiling it every iteration.

Other than that, this change looks great. Come talk to us on IRC when you get a chance so we can set up commit access.