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Copyright ©2015 CollabNet, Inc. All Rights Reserved.
Bringing Pull Request to Gerrit
A tale of feature development
Eryk Szymanski
Potsdam Engineering Office
CollabNet

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
CollabNet Facts
10,000+ customers,
proven in global
deployments as large
as 80,000 users and 1
billion commits
Leader in open-source
based application
lifecycle management,
version control, DevOps,
and collaboration
solutions
250 employees across
the globe
Founded in 1999; HQ
in South San
Francisco, CA
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
CollabNet Customers
Financials
Technology
Government
Other
Service Providers
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
CollabNet TeamForge - ALM Solution
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
TeamForge - Git/Gerrit Integration
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Our approach:
• Support Open Source
– Give back to the community
• If it is Gerrit core change, open source it
– Do not fork
• Stay as close to current Gerrit as possible
– It is ok to have patches on top of vanilla Gerrit
– But those are regularly rebased as Gerrit progresses
• Everything else goes into the plugins
Based on Gerrit 2.13.2 + some patches
and 6 proprietary plugins

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Git/Gerrit Integration - Features
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History ProtectionUsers & RBAC
Quality GatesReplication
Git LFS Support
Pull Request
Notifications

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Workflow
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yes
no

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request from Gerrit User Perspective
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What is a Pull Request?
– It is a merge commit pushed for review.
Does it mean it is possible to have a pull request in Gerrit?
– Yes, one can have a merge commit pushed for review.
But can I see a full diff to review the changes?
– Yes, it is possible since this patch got merged:
http://gerrit-review.googlesource.com/#/c/72092/
So what’s the big deal?
– No User Interface. Pull Request model is quite different
than Gerrit model and Gerrit UI does not support it.

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
From Pull Request User Perspective
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Will my branch appear in UI once I push it to remote?
– Yes, you can see it in Gerrit.
So where is my create pull request button?
– There isn’t any.
Oh, I thought you said there is a Pull Request feature in Gerrit.
Although technically speaking it is possible to use the Pull
Requests, from a user perspective there is still no such a feature
in Gerrit

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Motivation behind Pull Request
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• Pull Requests are popular
– Our customers ask for it
• General familiarity with the Pull Request model
– Easier onboarding for new TeamForge users
• Support feature branch development model
– Final big-bang review before merge
– One can even combine that with Gerrit model having both
Our goal was to deliver an intuitive Pull Request UI
to enable easy onboarding for people who are already familiar
with Pull Request and do not know Gerrit

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Implementation - User Interface Findings
•Gerrit UI is very powerful but hard to use for a novice
•Adding a new feature might not make it easier
•It is hard to maintain UI changes that are not upstream
•Working on UI with the community may slow us down
and does not give us full control over the UI
•The user experience degrades every time one have to switch
between different applications
•Not sure what to choose: GWT or PolyGerrit (at that
point of time)
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Implementation - User Interface Solution
• Seamless UI and Consistent flow for TeamForge Users
• One can use Pull Request or other Gerrit features without even seeing
Gerrit
• Everything happens in one place - TeamForge Code Browser
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Implement the UI in TeamForge Code Browser

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Implementation - REST API
• Gerrit Rest API:
– While it is doing great job for Gerrit, it is not always optimal in
delivering required data for our UI (i.e. Pull Request)
– Not versioned (and sometimes changes)
– No support for O-Auth authentication
• Solution:
– Come up with our own REST API
– It comes as a plugin and is specific for our needs
– Versioned and uses O-Auth for authentication
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Copyright ©2015 CollabNet, Inc. All Rights Reserved.Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Demo
Pull Request in Action

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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Code Browser - Branches
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Create Pull Request
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Created
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request In Review
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Reviewed
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Updated - Owner View
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Updated - Reviewer View
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Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Pull Request Ready To Be Merged
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Copyright ©2015 CollabNet, Inc. All Rights Reserved.Copyright ©2016 CollabNet, Inc. All Rights Reserved.
Thank you very much
Any Questions?