Git Introduction Tutorial

/tutorial/git
Thomas Rausch
thomas.rausch@tuwien.ac.at
Institute for Information Systems
Distributed Systems Group
TU Wien

http://git-scm.com

Of Linus and learning curves
“Linus is a guy who delights in being cruel to people …”

Of Linus and learning curves
“Linus is a guy who delights in being cruel to people …”
“His latest cruel act is to create a revision control system
which is expressly designed to make you feel less
intelligent than you thought you were” [1]
[1]: Tech Talk: Linus Torvalds on git - http://youtu.be/4XpnKHJAok8

What you should take from today

What you should take from today
git =

basics stages branch merge remotes advanced

$ git config --global user.name "Thomas Rausch"
$ git config --global user.email thomas@rauschig.org
Configure your user

$ git init
Initialized empty Git repository in /home/thomas/git-tutorial/.git/
Initialize an empty repository
$ git clone <repo> [<directory>]
Clone a remote repository

Check the status of your repository
$ git status
# On branch master
#
# Initial commit
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# README.md
# src/
nothing added to commit but untracked files present (use "git add" to track)
$ git status -sb
# Initial commit on master
?? README.md
?? src

$ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
# (use "git rm --cached <file>..." to unstage)
#
# new file: README.md
#
$ git add README.md
Start tracking files

Commit changes
$ git status
# On branch master
nothing to commit (working directory clean)
$ git commit -m "add readme file"
[master (root-commit) d4c59ff] add readme file
1 file changed, 3 insertions(+)
create mode 100644 README.md

View differences of current unstaged modifications
$ git diff --color
diff --git a/src/Main.java b/src/Main.java
index 66c8e93..dcdf6cb 100644
--- a/src/Main.java
+++ b/src/Main.java
@@ -1,5 +1,7 @@
class Main {
+ static int status = 0;
+
public static void main(String[] args) {
- System.exit(0);
+ System.exit(status);
}
}

Unstaging files
$ git status
# On branch master
# (use "git reset HEAD <file>..." to unstage)
#
# new file: src/HelloWien.java
# new file: src/HelloWorld.java
$ git reset HEAD src/HelloWien.java
$ git status
# On branch master
# (use "git reset HEAD <file>..." to unstage)
#
# new file: src/HelloWorld.java
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# src/HelloWien.java
#

Undoing local unstaged changes
$ git status
# On branch master
# Changes not staged for commit:
# (use "git add <file>..." to update what will be committed)
# (use "git checkout -- <file>..." to discard changes in working directory)
#
# modified: README.md
$ git checkout -- README.md
$ git status
# On branch master
nothing to commit (working directory clean)

Viewing the history
$ git log
commit 9c3cb834c43d67cc37b15e74b64dc830c1e78199
Author: Thomas Rausch <thomas@rauschig.org>
Date: Mon Oct 14 00:04:53 2013 +0100
modified readme file
commit d4c59ffd7e676dad6aef2cc244b87e3c579aa904
Author: Thomas Rausch <thomas@rauschig.org>
Date: Sun Oct 13 23:45:39 2013 +0100
add readme file
$ git log --graph --pretty=format:'%Cred%h%Creset %an: %s - %Creset %C(yellow)%d
%Creset %Cgreen(%cr)%Creset' --abbrev-commit -date=relative
* 9c3cb83 Thomas Rausch: modified readme file - (HEAD, master) (4 minutes ago)
* d4c59ff Thomas Rausch: add readme file - (24 minutes ago)
$ git log --oneline
9c3cb83 modified readme file
d4c59ff add readme file

working directory

working directory
staging area

working directory
staging area
repository

working directory
staging area
repository
git add

working directory
staging area
repository
git add
git commit

working directory
staging area
repository
git commit -a

working directory
staging area
repository
git reset HEAD <file>

working directory
staging area
repository
git reset HEAD <file> git checkout

$ git branch
develop
* master
new-feature
List branches

$ git branch
develop
* master
new-feature
List branches
Branch you have
currently
checked out

$ git checkout develop
Switched to branch 'develop'
Change into a branch

Manage branches
$ git branch <branch>
Create a new branch from the one you have currently checked out
$ git branch -m <oldbranch> <newbranch>
Rename a branch
$ git branch -D <branch>
Delete a branch

Merge branches
$ git checkout master
$ git merge topic
Merge the specified branch into the current branch (the one you have checked out)
Merges topic
into master

master
topic
master
topic

master
topic
master
topic
Fast-forward

topic
master
master, topic
Fast-forward

master
topic
master
topic
Recursive three-way

master
topic
A merge commit
with 2 parents
Recursive three-way

Conflicts

master

class Main {
public static void main(String... args) {
}
}
master

class Main {
}
}
master topic

class Main {
}
}
class Main {
static int status = 0;
System.exit(status);
}
}
master topic

class Main {
System.exit(0);
}
}
class Main {
}
}
class Main {
}
}
master topic

class Main {
System.exit(0);
}
}
class Main {
}
}
class Main {
}
}
class Main {
<<<<<<< HEAD
System.exit(0);
=======
>>>>>>> topic
}
}
master topic

master
develop
topic (features)

basics stages branch remotes advanced
master
merge

git branch develop
master
develop
merge

master
develop
merge

master
develop
feature
git branch featureX
merge

master
develop
feature
feature
git branch featureY
merge

master
develop
feature
feature
git merge featureX
merge

master
develop
feature
feature
git merge develop

master
develop
feature
feature
version 1.0

master
develop
feature
feature
git merge develop
downmerge

master
develop
feature
feature
version 2.0

master
develop
feature
feature

working directory
staging area
repository

working directory
staging area
local repository
remote repository

working directory
staging area
local repository
remote repository
working directory
staging area
local repository
working directory
staging area
local repository
developer developer developer

working directory
staging area
local repository
remote repository
working directory
staging area
local repository
working directory
staging area
local repository
developer developer developer
origin

working directory staging area local repository remote repository

git add/mv/rm
git commit
git commit -a
git reset <file>
git checkout <branch>

git push
git add/mv/rm
git commit
git commit -a
git reset <file>

git push
git fetch
git add/mv/rm
git commit
git commit -a
git reset <file>

git push
git fetch
git pull
git add/mv/rm
git commit
git commit -a
git reset <file>

Subversion
working
directory

Subversion
working
directory
remote
repository

commit
Subversion
working
directory
remote
repository

updatecommit
Subversion
working
directory
remote
repository

updatecommit
working
directory
Subversion Git
working
directory
remote
repository

updatecommit
local
repository
working
directory
Subversion Git
working
directory
remote
repository

updatecommit
local
repository
working
directory
remote
repository
Subversion Git
working
directory
remote
repository

Distribution models

Distribution models
Centralized workflow
origin

Distribution models
origin
GitHub Forking/Pull Request
dictator

Distribution models
origin
upstream
dictator developers
fork
origin

Distribution models
origin
Pull request
upstream
dictator developers
origin
fork

Distribution models
origin
Pull request
upstream
dictator developers
origin
fork
Many others

Managing remotes
$ git remote -v
origin git@github.com:thrau/openengsb-framework.git (fetch)
origin git@github.com:thrau/openengsb-framework.git (push)
upstream git@github.com:openengsb/openengsb-framework.git (fetch)
upstream git@github.com:openengsb/openengsb-framework.git (push)
$ git remote add <name> <url>
$ git remote rm <name>

Remote tracking branches
$ git branch -a

$ git branch -a
* master
my-local-feature
remotes/origin/master

$ git branch -a
* master
my-local-feature
originlocal
master
master,
origin/master

$ git branch -a
* master
my-local-feature
master
origin/master
originlocal
master

$ git push
master,
origin/master
originlocal
master

Delete remote branches
$ git push origin :branchname

Delete local tracking branches
$ git fetch origin --prune

Dealing with remote conflicts

$ git push origin master

master,
origin/master
originlocal
master

To ssh://thomas@localhost/home/thomas/git-remote
! [rejected] HEAD -> master (non-fast-forward)
error: failed to push some refs to 'ssh://thomas@localhost/home/thomas/git-remote'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Merge the remote changes (e.g. 'git pull')
hint: before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

$ git pull origin master

… fix merge conflicts ...

$ git commit -am "Merge remote branch 'master'"

$ git commit -am "Merge remote branch 'develop'"
Produces a
merge commit

$ git pull --rebase origin master
$ git rebase --continue
repeat
Rewrites the
history.

Rewriting history

Rewriting history
$ git rebase master
Rebase the current branch on to the tip of a different one

Rewriting history
master
topic
master
topic
$ git rebase master

Rewriting history
master
topic
“base”
$ git rebase master

Rewriting history
master
topic
$ git rebase master

Rewriting history
master
topic
“base”
* * **
* new commits
$ git rebase master

Rewriting history
master
topic * * **
Avoid changing
published histories!
$ git rebase master

Ups, I forgot something

$ git commit --amend -a
Add all your current changes to the previous commit

$ git commit --amend -m "new commit message"
Reword the last commit

$ git commit --amend -m "new commit message"
Reword the last commit
Avoid changing
published histories!

Pushing a rewritten history
$ git push --force origin <branch>
Danger zone! Overwrites the remote history with your local one. Remote commits may get lost!

When that merge came in like a wrecking ball
$ git merge --abort
$ git rebase --abort
Abort an initiated merge or rebase

Git tag
$ git tag
Show all tags
$ git tag -a v2.0
Tag the current commit with an annotation
Tag (mark) important points in the commit history, e.g. when a working version is released
$ git push origin --tags
Push tags to the remote

Ignoring files
Create a file in your repository (and add & commit it) named .gitignore, containing paths and
rules that tell git which files to ignore.
# Maven files
target/
bin/
# Eclipse project files
.project
.classpath
.settings
# Mac OS
.DS_Store
# IntelliJ IDEA files
*.iml
*.ipr
*.iws
.idea
# backup-files
*~

Writing good commit messages

Writing *bad* commit messages

”fix”

”fix”
“:(:(“

”fix”
“:(:(“
“changes”

”fix”
“:(:(“
“changes”
“it works!”

”fix”
“:(:(“
“changes”
“it works!”
“final commit”

”fix”
“:(:(“
“changes”
“it works!”
“final commit”
“Testing in progress ;-)”

”fix”
“:(:(“
“changes”
“it works!”
“final commit”
“TODO: write meaningful commit message”

”fix”
“:(:(“
“changes”
“it works!”
“final commit”
“TODO: write meaningful commit message”
“Your commit is writing checks your merge can't cash”

Write commit messages as if you're giving commands to the codebase

“Add DAO interfaces for Entities“

“Implement basic version of AddressDAO”

“Implement basic version of AddressDAO”
“Fix bug in delete method of UserDAO”
“Move package security to at.ac.tuwien.service”
“Add generated fxml files for UI”

Other great tutorials
●
Official Git Documentation
http://git-scm.com/doc
●
TryGit – An interactive Git tutorial
http://try.github.io
●
Git Immersion
http://gitimmersion.com/
●
Atlassian Git Tutorials
https://www.atlassian.com/git
●
Git Cheatsheet – Command categorisation
http://ndpsoftware.com/git-cheatsheet.html
●
LearnGitBranching
http://pcottle.github.io/learnGitBranching

Further reading
●
A successful Git branching model
http://nvie.com/posts/a-successful-git-branching-model/
●
Changing history, or How to Git pretty
http://justinhileman.info/article/changing-history
●
Reset Demystified
http://git-scm.com/blog/2011/07/11/reset.html
●
Avoiding Git Disasters: A Gory Story
http://randyfay.com/node/89
●
A Rebase Workflow for Git
http://randyfay.com/node/91

fin
Thanks for listening - Enjoy git!
Feedback appreciated
thomas.rausch@tuwien.ac.at

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