Harbormaster: continuous integration & patch building for GHC
When you use Arcanist to submit a diff, Phabricator will automatically trigger a build rule using an application called "Harbormaster". This application causes a build machine in the background to apply your patch and run sh ./validate. Afterwords, your diff will be updated with a status from Harbormaster about the build, including links to build logs and testsuite results.
The current status of the build is at the top. Phab:D162 is a good example:
Note that every time you run arc diff and update an existing review or create a new one, you'll trigger a build.
Harbormaster also builds GHC commits that have been pushed. You can see more on the Harbormaster application.
Note: You can use the word "[ci skip]" or "[skip ci]" by itself in the commit when you submit a diff or push something to skip builds. You may want to do this if you know your build will break, but you just want to post code.
Navigating the application UI
However, it's also useful to understand the application UI as well, so you can look through (or search for) previous builds.
Here we see builds for commits and builds for revisions. The metadata attached to each entry tells you this: things of the form Dabc - Diff xyz represent diffs, and things of the form rGHC: foo ... are for GHC commits.
Furthermore, a build is:
Building, which means the build is currently running. This status is marked by a blue color.
Failed, which means the build failed to run ./validate successfully. This status is marked by a red color.
Passed, which means the build ran ./validate just fine. This status is marked by a green color.