This document compares the decentralized version control systems Git and Mercurial. It discusses their histories, how they work in a decentralized manner without needing a central server, branching and merging workflows, and integration with development environments and tools. Key advantages noted are performance, flexibility, and popularity for Git, while Mercurial provides good multi-platform support and integration. The conclusion is that distributed version control systems are now essential for open source and will become standard in companies in the near future.

1. Systèmes de gestion de version décentralisés
Git & Mercurial
Sébastien Deleuze @sdeleuze
Loïc Frering @loicfrering

2. Historique
1990 CVS
2000
2002
2005
Bazaar

3. Les systèmes centralisés

4. Travail en mode connecté

5. Efficacité des équipes

6. Branches
Qui utilise régulièrement des branches avec Subversion ?

7. Branches
Quelques courageux, mais la plupart évitent à tout prix

8. Lenteurs !
.svn .svn
+ + .svn
.svn
.svn
+
=

9. Les systèmes distribués

10. Typologies des dépôts
Centralisés Décentralisés Distribués

11. Systèmes distribués
Pas besoin de réseau pour :
Faire un diff
Manipuler l'historique
Faire des commits
Gérer les branches

12. Principe

13. Performances

14. Easy branching

15. Hello World!

16. Initialisation du projet
$ git clone $ hg clone
https://loicfrering@github.com https://sdeleuze@bitbucket.org
/loicfrering/hello.git /sdeleuze/hello
Initialized empty Git destination directory: hello
repository in updating to branch default
/home/hello/.git/ 0 files updated, 0 files
warning: You appear to have merged, 0 files removed, 0
cloned an empty repository. files unresolved
$ cd hello $ cd hello
$ tree -aL 1 $ tree -aL 1
. .
└── .git └── .hg
1 directory, 0 files 1 directory, 0 files

17. HelloWorld.java
$ vim HelloWorld.java
$ cat HelloWorld.java
public class HelloWorld {
public static void main(String[] args) {
HelloWorld hello = new HelloWorld();
System.out.println(hello.sayHello());
}
public String sayHello() {
return "Hello World from Java!";
}
}

18. Track HelloWorld.java
$ git status -s $ hg status
?? HelloWorld.java ? HelloWorld.java
$ git add HelloWorld.java $ hg add HelloWorld.java
$ git status -s $ hg status
A- HelloWorld.java A HelloWorld.java

19. Premier commit
$ git commit -m "Hello Java" $ hg commit -m "Hello Java"
[master (root-commit) 8866129]
Hello Java
1 files changed, 10
insertions(+), 0 deletions(-)
create mode 100644
HelloWorld.java

20. HelloWorld.php
$ vim HelloWorld.php
$ cat HelloWorld.php
<?php
class HelloWorld
{
public function sayHello()
{
return 'Hello World from PHP!';
}
}
$hello = new HelloWorld();
echo $hello->sayHello() . PHP_EOL;

21. Second commit
$ git add HelloWorld.php $ hg add HelloWorld.php
$ git commit -m "Hello PHP" $ hg commit -m "Hello PHP"
[master db9dd3c] Hello PHP
1 files changed, 11
insertions(+), 0 deletions(-)
create mode 100644
HelloWorld.php

22. Nouvelle fonctionnalité

23. HelloWorld.java
$ vim HelloWorld.java
$ cat HelloWorld.java
public class HelloWorld {
public static void main(String[] args) {
HelloWorld hello = new HelloWorld();
System.out.println(hello.sayHello("LyonJUG"));
}
public String sayHello(String name) {
return "Hello " + name + " from Java!";
}
}

24. HelloWorld.php
$ vim HelloWorld.php
$ cat HelloWorld.php
<?php
class HelloWorld
{
public function sayHello($name)
{
return 'Hello ' . $name . ' from PHP!';
}
}
$hello = new HelloWorld();
echo $hello->sayHello('LyonJUG') . PHP_EOL;

25. Staging area
$ git status -s $ hg status
-M HelloWorld.java M HelloWorld.java
-M HelloWorld.php M HelloWorld.php
$ git add HelloWold.java $ hg commit -m "Hello2 Java&PHP"
$ git status -s
M- HelloWorld.java
-M HelloWorld.php

26. Staging area

27. Staging area
$ git status -s
M- HelloWorld.java
-M HelloWorld.php
$ git status
# On branch master
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# modified: HelloWorld.java
#
# Changed but not updated:
# (use "git add <file>..." to update what will be committed)
# (use "git checkout -- <file>..." to discard changes in working
directory)
#
# modified: HelloWorld.php
#

28. Staging area
$ git commit -m "Hello2 Java"
[master 99eb692] Hello2 Java
1 files changed, 3 insertions(+), 3 deletions(-)
$ git status -s
-M HelloWorld.php
$ git add HelloWorld.php
$ git commit -m "Hello2 PHP"
[master c262c26] Hello2 PHP
1 files changed, 3 insertions(+), 3 deletions(-)

29. Historique
$ git log --pretty=oneline -- $ hg log
abbrev-commit changeset: 2:5eb829edb1a0
c262c26 Hello2 PHP tag: tip
99eb692 Hello2 Java user: sdeleuze
db9dd3c Hello PHP date: Mon Sep 20 ...
8866129 Hello Java summary: Hello2 Java and
PHP
changeset: 1:8e3a9a10985d
user: sdeleuze
date: Mon Sep 20 ...
summary: Hello PHP
changeset: 0:cfeb26b9662d
user: sdeleuze
date: Mon Sep 20 ...
summary: Hello Java

30. Et Ruby ?
Travaillons dans une branche !

31. Branche
$ git branch $ hg branch
* master default
$ git branch helloruby $ hg branch helloruby
helloruby marked working directory as
* master branch helloruby
$ git checkout helloruby $ hg branch
Switched to branch 'helloruby' helloruby
$ git branch
* helloruby
master

32. hello_world.rb
$ vim hello_world.rb
$ cat hello_world.rb
class HelloWorld
def sayHello(name)
"Hello " + name + " from Ruby!"
end
end
hello = HelloWorld.new
puts hello.sayHello("LyonJUG")

33. Troisième commit
$ git status -s $ hg status
?? hello_world.rb ? hello_ruby.rb
$ git add hello_world.rb $ hg add hello_world.rb
$ git commit -m "Hello Ruby" $ hg commit -m "Hello Ruby"
[helloruby 149af0e] Hello Ruby
1 files changed, 8
insertions(+), 0 deletions(-)
create mode 100644
hello_world.rb

35. Agilité : correction isolée
$ git branch $ hg branch
* helloruby helloruby
master $ hg update default
$ git checkout master 0 files updated, 0 files merged,
Switched to branch 'master' 1 files removed, 0 files
$ ls unresolved
HelloWorld.java HelloWorld.php $ ls
$ vim HelloWorld.java HelloWorld.java HelloWorld.php
$ vim HelloWorld.php $ vim HelloWorld.java
$ git add . $ vim HelloWorld.php
$ git commit -m "Hello3 $ hg commit -m "Hello3 Java&PHP"
Java&PHP" created new head
[master 71832b3] Hello3 Java&PHP
2 files changed, 2
insertions(+), 2 deletions(-)

36. Agilité : reprise du travail
$ git branch $ hg branches
helloruby default 4:d4455bac12b2
* master helloruby 3:5c5b732498bf
$ git checkout helloruby $ hg update helloruby
Switched to branch 'helloruby' 3 files updated, 0 files merged,
$ vim hello_world.rb 0 files removed, 0 files
$ git commit -a -m "Hello3 Ruby" unresolved
[helloruby bb94cb2] Hello3 Ruby $ vim hello_world.rb
1 files changed, 1 $ hg commit -m "Hello3 Ruby"
insertions(+), 1 deletions(-)

37. Merge
$ ls $ ls
hello_world.rb HelloWorld.java hello_world.rb HelloWorld.java
HelloWorld.php HelloWorld.php
$ git checkout master $ hg update default
Switched to branch 'master' 2 files updated, 0 files merged,
$ ls 1 files removed, 0 files
HelloWorld.java HelloWorld.php unresolved
$ git merge helloruby $ ls
Merge made by recursive. HelloWorld.java HelloWorld.php
hello_ruby.rb | 8 ++++++++ $ hg merge helloruby
1 files changed, 8 1 files updated, 0 files merged,
insertions(+), 0 deletions(-) 0 files removed, 0 files
create mode 100644 unresolved
hello_ruby.rb (branch merge, don't forget to
$ ls commit)
hello_world.rb HelloWorld.java $ ls
HelloWorld.php hello_world.rb HelloWorld.java
HelloWorld.php

38. Log
$ git log --graph --pretty=oneline $ hg log -G
--abbrev-commit @ changeset: 6:491d950b55ac
* 7a390ee Merge branch 'helloruby' | tag: tip
| | | summary: Merge
| * bb94cb2 Hello3 Ruby | |
| * 149af0e Hello Ruby | o changeset: 5:89f865402568
* | 71832b3 Hello3 Java&PHP | | branch: helloruby
|/ | | summary: Hello3 Ruby
* c262c26 Hello2 PHP | |
* 99eb692 Hello2 Java o | changeset: 4:d4455bac12b2
* db9dd3c Hello PHP | | parent: 2:5eb829edb1a0
* 8866129 Hello Java | | summary: Hello3
| |
o | changeset: 2:5eb829edb1a0
| | summary: Hello2 Java
| |
| o changeset: 3:5c5b732498bf
|/ branch: helloruby
| summary: Hello Ruby

39. Push
$ git push origin master $ hg push
Counting objects: 26, done. pushing to
Delta compression using up to 2 https://sdeleuze@bitbucket.org/sde
Compressing objects: 100% leuze/hello
(25/25), done. searching for changes
Writing objects: 100% (26/26), adding changesets
2.56 KiB, done. adding manifests
Total 26 (delta 10), reused 0 adding file changes
(delta 0) added 8 changesets with 42 changes
To to 3 files
https://loicfrering@github.com/lo
icfrering/hello.git
* [new branch] master -> master

40. Pull
$ git pull origin master $ hg pull -u
remote: Counting objects: 3, pulling from
done. https://sdeleuze@bitbucket.org/sd
remote: Compressing objects: 100% eleuze/hello
(2/2), done.
remote: Total 2 (delta 0), reused searching for changes
0 (delta 0) adding changesets
Unpacking objects: 100% (2/2), adding manifests
done. adding file changes
From added 1 changesets with 1 changes
git://github.com/loicfrering/hell to 1 files
o.git 1 files updated, 0 files merged,
* 7a390ee..c84376b master -> 0 files removed, 0 files
origin/master
unresolved
Updating 7a390ee..c84376b
Fast-forward
HelloWorld.py | 8 ++++++++
1 files changed, 8
insertions(+), 0 deletions(-)
create mode 100644 HelloWorld.py

41. Intégration au poste
de développement

42. Console versus IHM
Constat :
- SVN = IHM d'abord, ligne de commande après
- Git/Mercurial = ligne de commande d'abord, IHM après

43. Intégration système Mercurial
 Excellent support multi-plateformes
 Support des proxy en entreprise
 Intégration Windows TortoiseHg
 hg serve très utile

44. Intégration système Git
 Intégration Windows
 msysGit / GitCheetah
 Cygwin
 TortoiseGit
 Support Windows un cran en dessous
 Support des proxy en entreprises

45. : MercurialEclipse
 Stable
 Performant
 Support complet

46. : EGit
 La Fondation Eclipse passe sous Git
 Basé sur JGit
 Part de loin mais progresse vite
 A terme, intégré nativement à Eclipse

47. : support Mercurial
 Support natif
 Bonne intégration
 Visualisation des branches un peu limitée

48. : NBGit
 Plugin encore jeune, mais utilisable
 Visualisation des branches
 Projet peu actif

49. Projets

50. Projets sous Mercurial

51. Projets sous Git

53. Forges

54. Forges "classiques"

64. Forges en entreprise
2 solutions :
 FaaS : Forge as a Service
 Forge interne
Intégration :
 Comptes utilisateurs
 Maven
 Intégration continue

65. Workflows

66. Systèmes centralisés

67. Open Source

68. Entreprise
Architecte
Resp qualité
Lead dev

69. Gestion avancée des branches
Développement
Qualification - Recette
Intégration continue Production

70. NoSQL ?

71. NoSQL !
Comme solution de persistence :
 Gestion des versions
 Gestion des conflits
 Arborescence
 Stockage fichiers binaires
 Réplication

72. Conclusion

73. Synthèse
 Performances
 Multi-platforme
 Branches
 Formation
 Support proxy
 Intégration IDE
 Souplesse
Popularité

74. 2010 : les DVCS sont incontournables
dans le monde Open Source
2011 : les DVCS seront
incontournables en entreprise

75. Liens
Git Reference Hg Init
Pro Git Mercurial: The definitive guide
Git community book Bitbucket
GitHub
Analysis of Git and Mercurial
DVCS: A Not-So-Quick Guide Through
Why Git is better than X where X is one of hg, bzr, svn, perforce
Notre interview sur Git et Mercurial par Agnès Crepet des JDuchess

76. Crédits
Scott Chacon : Why git is better than X
Scott Chacon : Git 101
Chris Wanstrath : Git: The Lean, Mean, Distributed Machine
Vincent Driessen : A successful Git branching model
Curtis Newton : Green light = Go / Flickr
Gource : Software version control visualization