What is Phabricator
Phabricator is a software development collaboration tool and includes features such as code review and repository browsing. Facebook runs a Phabricator instance at reviews.facebook.net, which is where all pull requests on GitHub get sent to be reviewed by the HHVM team.
When you submit a pull request to HHVM, you will notice a comment from facebook-github-bot appear shortly after, with a link to a newly-created Phabricator review:
You do not have to register for Phabricator, although in order to discuss changes this allows you to directly converse with the change reviewers. To register, simply click the "standby" icon top right of Phabricator, and register using your GitHub account - this allows all future changes from your account to be created in your name (rather than facebook-github-bot). This means that when you go to reviews.facebook.net/differential/query/authored/, you will see all your changes in one place.
You might notice the following message on your review:
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