Multi-Author Collaboration:
writing papers/code with Git

Idiap Research Institute
2010-11-29

Rémi Emonet

Objective of the Presentation

• Version Control Systems
• concepts
• “rules”
• Practical Git
• basic knowledge
• writing a latex paper
• Interrupt me when necessary!

Survey

• Who already knows Git?


• Who knows any of these?
• CVS, Subversion,
• Mercurial, Baz, GnuArch

Background

• Warning: not a Git expert
• for Git by a git, ask Linus
• the gittutorial
• many other resources on the web
• My trajectory
• cp
• date
• tar
• “rameute.sh”
• (mail/diff)
• cvs, svn, GnuArch, bazaar
• git

Starting with Git

• Initializing your project

git init

• What's up?

git status

• Deciding what is relevant

git add file1 file2 …
git commit

Let's try it

cp -r base 2011cvpr ; cd 2011cvpr

git init

git status
git add     2011cvpr.tex  cvpr.sty
git status
git commit
git status

... and more

Recap

• Beginning

git init
git add ...
git commit [-m ...]

• Working

git status
git add ...
git commit [-m ...]

Recap 2

• Clean projects: ignoring files
• .gitignore file(s)
• blabla.*, !blabla.my_precious, *~
• What did I just modify?

git status
git diff [...]

• What happened?

git log

• See also: git reset

Nota Bene (vs CVS, Subversion)

• Local commit
• commit everywhere (train, plane, here)
• merge with 0-stress
• ! backup
• By-project commit
• Need to “git add” modifications

GUI for Git

• Bundled with git: git gui

• Many others (qgit, GitX, tortoisegit)

Customizing Git

• Introducing yourself

git config --global user.name  "John Doe"
git config --global user.email john@doe.com

• Fancy colors and shortcuts

git config --global color.ui true

git config --global alias.st status
git config --global alias.ci commit

• Configuration in ~/.gitconfig

About History

• Remember git log?
• Each commit is written in stone
• parent(s) commit
• modifications
• sha1sum (e.g.    cb6dc3cb1f4f5eb15c1d9b2b25ae741cd73c0554)


• can be diff'ed against

git diff cb6dc3

• can be retreived

git checkout cb6dc3

Back to the Future: rewriting the past

• gitk, the “git gui” of history
• Let's go…

Recap

• Branch
• label for a commit
• automatically follows on commit
• Always commit before merging
• Use of “sha1” or branch-name (e.g. brrrr)
• Shortcuts

cb6dc3, brrrr, HEAD,
HEAD^, HEAD^^, HEAD^1, HEAD^42
cb6dc3^42, tagggg

Recap 2

• Moving in the history

git checkout sha1-or-branch-name

• Creating a new branch at current position

git checkout -b new-branch-name

• Merging “brrrr” into “master”

git checkout master
git merge brrrr

Recap 3

• Automatic git merge ⇒ automatic commit
• On conflicting git merge
• (partial merge)
• solve conflict
• git add
• git commit


• Exploring history
• git log
• gitk [--all]

Following a Repository

• Getting a full copy of a repository

git clone ~bob/repo/cvpr [my2011cvpr]

• Pulling latest modifications
    (like “cvs/svn update”)

git pull [origin master]

• Pulling = fetch + merge

git fetch
git merge

Distributed Version Control System

• Full local repository
• in-plane commit
• 0-stress merge
• Pull (fetch+merge)
• from the “origin”

git pull

• from any “remote”

git remote add john-repo ~john/…

git pull john-repo master
git pull john-repo experiment

Creating a Shared “Centralized” Repository

• Concepts
• “bare” repository (no classical files)
• “shared” access
• From scratch

git --bare init --shared=group

• From an existing repository

git clone --bare /home/john/repo/cvpr [...]
cd ....
git config core.sharedRepository group

Contributing to a Shared Repository

• Init: git clone ...
• Hack hack hack
• git commit hack git commit hack git commit
• Merge and solve conflicts: git pull
• Share: git push [origin master]
• (see also: git rebase)

Team Work

• Distributed or Centralized?
• Shared branches?
• Never break the “master”
• File formatting
• do not reformat sources (.tex, ...)
• 1 sentence = 1 line ?

Last Things

• Working Over the Network
• nfs
• ssh, http, “git”
• svn, cvs


• Reminder
• always commit before merge
• backup your repository (NAS ✓)