= Model Support in Gerrit
:backend: slidy
:max-width: 70em

[[title-page]]
== Model Support in Gerrit?

== Model Support in Gerrit?

* Gerrit Introduction
* Challenges with Models
* Model Support in Gerrit?

== About Me

image:../../img/edwin.png[height=600]

[[title-page]]
== Gerrit Introduction

== Gerrit Introduction

* What is Gerrit?
* Gerrit Workflow
* Benefits

== Gerrit

https://code.google.com/p/gerrit/

* Open Source
** Large Community
** Apache License, Version 2.0

* Used by
+
image:../../img/logos.png[height=400]

== Gerrit

*What is Gerrit?*

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* Git Server
+
image:../../img/gerrit-server.png[height=400]

[[review-site]]
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--
Review Site:

image:../../img/review-site.png[height=400]
--

== Gerrit

*Gerrit Features*

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* Code Review
+
image:../../img/code-review.png[height=400]

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[[acl]]
--
* Access Control
+
image:../../img/default-access-rights.png[height=400]
--

== Gerrit Workflow

== Gerrit Workflow

image:../../img/workflow-1.png[height=600]

== Gerrit Workflow

image:../../img/workflow-2.png[height=600]

== Gerrit Workflow

image:../../img/workflow-3.png[height=600]

== Gerrit Workflow

image:../../img/workflow-4.png[height=600]

== Gerrit Workflow

image:../../img/workflow-5.png[height=600]

== Gerrit Workflow

image:../../img/workflow-6.png[height=600]

== Benefits of Code Review with Gerrit (1)

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* Collaboration to find Best Solution
+
[small]#-> eliminate bugs early#

* Discussions on Code Level
+
[small]#-> very efficient#

* Transparent and Open Development Process
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[small]#-> everyone can take part and comment/vote#
+
[small]#-> discussions are preserved#

* Learn by Reading Code
+
[small]#-> become a better developer#

== Benefits of Code Review with Gerrit (2)

[role="incremental"]
* Code Review is integrated into the Development Process

* Works well across Locations and Time Zones

* Easy Integration with Jenkins
+
[small]#-> automatic verification#

* Results in
** Clean Commits
** Good Commit Messages
** Clean History

[[title-page]]
== Challenges with Models

== Challenges with Models

* The Entity Challenge
* The Review Challenge
* The Comment Challenge
* The Merge Challenge

== The Entity Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|=====

== The Entity Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Gerrit operates on Files|image:../../img/conflict.png[height=80]|Mapping of Model Entities to Files may not be 1:1
|=====

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* File List on Change Screen
+
[small]#-> unchanged files are not shown, model entities which are
mapped to n files may be shown incompletely#
+
image:../../img/file-list.png[height=200]

== The Entity Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Gerrit operates on Files|image:../../img/conflict.png[height=80]|Mapping of Model Entities to Files may not be 1:1
|=====

* Review Navigates from File to File
+
image:../../img/side-by-side-diff-view.png[height=200]

== The Review Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Review on File Content|image:../../img/conflict.png[height=80]|Review
Visual Model Representation, is File Representation readable?
|=====

== The Review Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Review on File Content|image:../../img/conflict.png[height=80]|Review
Visual Model Representation, is File Representation readable?
|Diff-Highlighting is Text-Based|image:../../img/conflict.png[height=80]|
Specialized Model-Diff
|=====

== The Review Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Review on File Content|image:../../img/conflict.png[height=80]|Review
Visual Model Representation, is File Representation readable?
|Diff-Highlighting is Text-Based|image:../../img/conflict.png[height=80]|
Specialized Model-Diff
|Minimal Diff|image:../../img/conflict.png[height=80]|Large File-Based
Diff due to Reformatting/Resturcturing done by the Model Tool
|=====

== The Review Challenge

* Side-By-Side Diff
+
image:../../img/side-by-side-diff.png[height=250]

== The Review Challenge

* Unified Diff
+
image:../../img/unified-diff.png[height=500]

== The Comment Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Comments on File Content|image:../../img/conflict.png[height=80]|Comments on Model Entities,
can they be mapped to inline comments back and forth?
|=====

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* Inline comments
+
image:../../img/inline-comment.png[height=200]

== The Merge Challenge

[frame="none",grid="none",halign="center",valign="center",width="65%"]
|=====
|image:../../img/diffy.png[height=150]||image:../../img/papyrus.png[height=150]
|Conflict Detection on File Level|image:../../img/conflict.png[height=80]|
Conflicts on Model Entities, Model may be broken after clean merge.
|=====

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* Pessimistic Locking is *NOT* possible.

* Submit/Merge Strategy
+
[small]#-> can be controlled per change from Prolog#
+
image:../../img/submit-type.png[height=200]

[[title-page]]
== Model Support in Gerrit?

== Model Support in Gerrit?

* Reviewable Models
* A Simple Example
* Can we do better?

== Model Support in Gerrit?

image:../../img/gerrit-model-question-1.png[height=200]

[[question-2]]
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image:../../img/gerrit-model-question-2.png[height=200]

[[answer]]
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* Make the source human readable.
* Map 1 model entity to 1 file (unit of conflicts)

== A Simple Example

Project Documentation in Gerrit
(link:https://gerrit-review.googlesource.com/#/admin/projects/plugins/x-docs[xdocs plugin])

image:../../img/project-documentation.png[height=600]

== A Simple Example

image:../../img/project-documentation-preview-link.png[height=600]

== A Simple Example

image:../../img/project-documentation-preview.png[height=600]

== A Simple Example

Possible *Future* Extension:

* Render Side-By-Side Diff / Unified Diff based on HTML comparison
+
image:../../img/html-diff.png[height=400]

[[title-page]]
== Better Model Support in Gerrit?

== Better Model Support in Gerrit?

1. Extend Gerrit
2. Model Support as Gerrit Plugin

== Better Model Support - Extend Gerrit

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* Open Source Project

* Model support currently not a focus topic for Gerrit Community,
+
no plans to pro-actively support models

* Issues of Diffing and Merging must be solved
+
beforehand by the Modelling Technology

* Major Refactorings in Gerrit are difficult to get in

== Better Model Support - Gerrit Plugin

What is possible *today*?

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* Show a Model Preview
+
[small]#-> from upcoming Gerrit 2.11, as done by xdocs plugin#

* Add Custom Screens

* Add Menu Entries

* Add Button to Change Screen
+
[small]#-> e.g. "Model View" to switch to a Model-Aware Change Screen#

* Model Validation on Push
+
[small]#-> better to be done in Jenkins#

* Access to Git Repositories
+
[small]#-> change Git configuration#

[role="incremental"]
Possible *Future* Extensions:

[role="incremental"]
* Custom Rendering of Diff
* Custom Submit/Merge Strategies

== Better Model Support - Gerrit Plugin

What is possible today?

* Show a *Model Preview*
+
[small]#-> from upcoming Gerrit 2.11, as done by xdocs plugin#

* Add Custom Screens

* Add Menu Entries

* Add Button to Change Screen
+
[small]#-> e.g. "Model View" to switch to a Model-Aware Change Screen#

* Model Validation on Push
+
[small]#-> better to be done in Jenkins#

* Access to Git Repositories
+
[small]#-> change Git configuration#

Possible Future Extensions:

* Custom *Rendering of Diff*
* Custom *Submit/Merge Strategies*

[[title-page]]
== Questions?

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