Need some way of translating the line in a file to the `position` param for a pull request review

[cweagans]

Most of the code style/static analysis tools that I use work on an entire file, and not just a diff. It would be awesome to be able to run a code style check on whatever file changed, and then use this tool to automatically add a comment to the line in question inline in the PR.

Right now, there's not really a great way translate between a line in a file and the position param that Github needs in e.g. a bash script that's calling this utility, so I'm wondering if that might be easier in Go as a helper command or something. If this utility isn't the right place for that translation to happen, do you have any suggestions for other utilities that might handle that translation?