Phabricator for Ubers

Created by Aiden Scandella

What I'll Cover

• Arcanist, a.k.a. arc — CLI
• Differential — Code Review
• Maniphest — Task Integration
• Sample workflow

What I Won't Cover

• Git Basics
• Setting up arc (see: new developer quickstart)
• Phabricator's meme syntax
• Any of the other apps

Coming from GitHub

GitHub: Pull requests (commits and branches)

Phabricator: Revisions (everything is a diff)

Why does that matter?

• For basic usage, it doesn't

• Instead of pushing a branch and opening a pull request, you simply run arc diff

Hello, arc

$ git checkout -b add-toaster-oven
$ emacs
$ git commit
$ arc diff

Addressing review feedback

• Make your changes
• Create a new commit on top of your previously reviewed change
• Run arc diff again
• Note the lack of force-pushing

When You Get Lost

• When a rebase leaves you in a strange state
• When you're working on multiple feature branches
• Use arc which to get a sense of your surroundings

$ arc which

arc which

Updating an existing revision

• If you lose your commit message link and your tree changes
• Use the --update revision-id

$ arc diff --update D123

Changing what's in the diff

• By default, looks at all local changes between your upstream branch (e.g. origin/master) and HEAD
  • Roughly equivalent to:

    $ git diff $(git merge-base origin/master HEAD)..HEAD

  • This confuses some people
• To override, specify a base reference (branch name, SHA, symbolic ref):

  $ arc diff <base-ref>

• We set a global default, overriding upstream behavior, like this:

  $ arc set-config base "git:merge-base(origin/master), arc:prompt"

Complex scenario

I'm working off a co-worker's topic branch feature-a, I can send just my changes up for review:

$ git fetch && git checkout feature-a
$ git checkout -b feature-b
$ emacs
$ git commit
$ arc diff feature-a

You get two knobs

• Only two things you usually want to tweak
• The base, which specifies where your diff begins
• Your differential revision (e.g. D456), which can be manually specified with

  $ arc diff --update D456

In review

• Creates or updates a diff between HEAD and your upstream branch
  • If you're going to be pushing your branches pre- code-review, I highly recommend overriding your default base
• If it recognizes an existing revision, updates
• Otherwise it creates a new one
• Behavior can be overriden by using --update D123 or specifying a base-ref

What's changed for reviewers?

• Diff between versions of a revision (my FAVORITE)
  • What's changed since the last time I looked at this?
• More explicit actions
  • Comment
  • Request Changes ✘
  • Accept Revision ✔

Maniphest Tasks

• Like all objects in Phabricator, you can reference T<maniphest ID> to create a bi-directional link
• Use special 'Fixes TXXX' to automatically mark a task resolved when the revision is landed

Auto-closing tasks

And now, some tibdits

Turn down the noise

By default, you get an email from Phabricator for every action you're a part of, including actions you trigger.

To turn this off, go to your email preferences page

But I liked getting all that email...

With GitHub, you get an email for every PR and every individual comment on every repository.

With Phabricator, it's much more targeted: only reviewers and CCs are notified of new diffs and comments.

If you want to opt-in, you can set up a herald rule.

Herald in action

Where can I test this out?

• Make sure you have your ssh forwarding set up

$ git clone gitolite@code.uber.internal:testing
$ cd testing
$ # arc diff to your heart's content

Questions?

Cool. And now, a demo