Monday, September 7, 2009

Code Review for Git

I wanted to find a way to contribute to projects that I couldn't pair on, and to be able to scan a project for possible changes without sitting down and taking up someone's time. Sounded a lot like automated code review, so I had a look around at available code review tools. There are a few available - Review Board, Smart Bear and Crucible among them. I know Atlassian and generally like their products so I decided to install Crucible and give it a try.

There were a few confusing configuration problems. Until I read the documentation more closely (at all?) I wasn't aware that the beta Git plugin only worked against local git repositories, and I had to change a configuration file to convince Crucible that Ruby files should be treated as text instead of binaries, but once I got past these problems I clearly had a powerful tool for distributed, multi-party code reviews available to me.

So I created a review, looked at some code, and saw one thing that I would change. I wrote the comment, but things just felt wrong. It had taken me a while to type to comment (I'm not the world's fastest typist, but nor am I the slowest), and it felt like a waste of time. It would have been far faster to make the change and annotate the corresponding commit, but what I had was a code review tool, not an editor. Something wasn't working for me.

When I do a code review I want to achieve two things - I want to fix the code and I want to educate someone (where that someone may be me, if I wrote the original code). What I really wanted was something (an editor) that would let me focus on changes between versions, but let me change the latest version and save it. My VCS could store the comments against the (small) changes and I could point people to the VCS history to see what I'd done, potentially using the same tool.

After looking at a few different tools last night I've settled on Changes. Changes lets you compare directory structures and files, and it comes with some Ruby scripts that will help you retrieve specific revisions from Git, drop them into temp directories and review the differences. I've modified the script to use the current directory if you're comparing to HEAD, so that changes to the head are saved directly to disk and can be committed.

Here's my process:

1) Use GitX to determine the revision I want to use as the base
2) Use changes to view the differences
3) Incrementally work through the files either making changes or excluding the files.

I've created a (silent) video that shows me working through one review. I only make one small change, so it's mostly scrolling and excluding. One small point - the video uses an older version of my Ruby script that created a temp directory even if you were looking at HEAD, so changes were lost. I've fixed that in this version.

I saw some comments that Changes was rather expensive (US$49.99), but it's really cheap compared to many code review tools so I'm pretty happy with this approach.

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