A practical step-by-step guide to Git, taking you through each phase of a project and explaining the use of Git at each step of the development process. Expect lots of how-to, but also some how-not-to, to avoid going down the wrong path.

1. Practical git for developers
(aka 'Git for beginners')
Wim Godden
Cu.be Solutions
@wimgtr

2. Who am I ?
Wim Godden (@wimgtr)

3. Where I'm from

4. Where I'm from

5. Where I'm from

6. Where I'm from

7. Where I'm from

8. Where I'm from

9. My town

10. My town

11. Belgium – the traffic

12. Who am I ?
Wim Godden (@wimgtr)
Founder of Cu.be Solutions (http://cu.be)
Open Source developer since 1997
Developer of PHPCompatibility, OpenX, PHPConsistent, ...
Speaker at Open Source conferences

13. Who are you ?
Developers ?
CVS ?
SVN ?
TFS ?
Git ?

14. What is git ?
Git is a file system
with a Version Control System on top of it

15. Git's file structure
Commit
tree
author_info
parent
Tree
README.MD
LICENSE
index.php
Blob
datadatadata...
Blob
datadatadata...
Blob
datadatadata...
6d3af... 8a3ea...
901a3...
4a39c...
e3231...
8a3ea... 901a3...
4a39c...
e3231...

16. What is git ?
Git is a file system
with a Version Control System on top of it

17. What is git ?
Git is a distributed file system
with a Version Control System on top of it

18. (Almost) everything is local
Clone = copy of entire repository
Work offline :
Perform a diff
View file history
Commit changes (!)
Create, merge or switch branches
etc.
Only push/pull are not local

19. (Almost) everything is immutable
Immutable = doesn't change
Once placed in git, it stays there
Even if you delete files

20. Differences with SVN
SVN keeps diffs between versions
Git keeps full snapshots
Commit #1
tree
author_info
parent
Tree
README.MD
Commit #2
tree
author_info
parent
Tree
README.MD
index.php
Commit #3
tree
author_info
parent
Tree
README.MD
LICENSE
index.php

21. Differences with SVN
SVN is centralized
↔ Git is distributed
An SVN commit → shared with everyone
↔ A Git commit is local
SVN has revision increments
↔ Git has SHA1 hashes to identify objects
(commits, trees, blobs, ...)

22. Basic git – config
$ git config --global user.name "Wim Godden"
$ git config --global user.email "wim.godden@cu.be"
$ git config --global core.editor vim
$ git config --global core.autocrlf input
$ git config --global core.autocrlf true
$ git config --global color.ui true
(on Linux)
(on Windows)

23. Basic git - .gitignore
Allows you to specify files to ignore
Can be specific to repository
Hint : set up a global .gitignore for :
thumbnail.dat
desktop.ini
.DS_Store
Your local editor's files
…

24. Create a repo
$ git init
$ tree .git
.git/
├── branches
├── config
├── description
├── HEAD
├── info
│ └── exclude
├── objects
│ ├── info
│ └── pack
└── refs
├── heads
└── tags

25. .git directory
config – Configuration file
refs/heads/... - branches
refs/tags/... - tags
refs/remotes/... - remotes
objects/... - the actual objects
HEAD – the current working space, points to one of branches

26. git clone
Creates a repository from an existing repository
git clone https://someplace.com/repo.git <somefolder>
Original repository is called 'origin'
→ This is called a 'remote'

27. Git flow
Working directory
Staging area
Repository
Remote(s)
Add
Commit
Push

28. git status
Simple command
Explains in clear language what's going on
Use it, use it, use it, ...

29. Git flow
Working directory
Staging area
Repository
Remote(s)
Add
Commit
Push

30. git add
Add file in current state to the staging area
Can be new file
Can be modification
git add -A stages all
git add . stages new and modified, but no deletions
git add -u stages modified and deleted, but no new files

31. git reset
Unstage changes
Revert to older commit version
Beware : dangerous command !

32. Remove files from repository
2 ways :
Delete, then rm
Delete the file from working directory
git rm <filename>
Commit
Just rm
git rm <filename>
Commit
Accidentially deleted ?
→ git checkout -- <filename>

33. Git flow
Working directory
Staging area
Repository
Remote(s)
Add
Commit
Push

34. git commit
Creates a new version
Based on the staging area
Commits on local repository only
Commit #1
tree
author_info
parent
Tree
README.MD
Commit #2
tree
author_info
parent : #1
Tree
README.MD
index.php
Commit #3
tree
author_info
parent : #2
Tree
README.MD
LICENSE
index.php
HEAD

35. git log
Shows each commit with SHA1 hash
→ hash can be used with other commands
-p gives a diff view

36. git diff
No params : default diff output
git diff --staged : diff with what's been staged

37. Clone, add, commit and push
C1
Remote originLocal repository
C2
master
C1 C2
origin/master
1 2
C1 C2
origin/master
C3
master HEAD
master HEAD1
2 C1 C2
master
C1 C2
origin/master
C3
master HEAD
3
3
C1 C2
master
C3

38. Working with remotes
git push
→ Send locally commited changes to the remote repository
git fetch/pull
→ Retrieve changes from the remote repository

39. Fetch, merge and pull
Remote originLocal repository
C1 C2
origin/master
1 2
C1 C2
origin/master
C3
master HEAD
master HEAD
1
C1 C2 C3
master HEAD
2
3
C1 C2
master
C3C2
origin/master 3

40. git fetch + merge vs git pull
git fetch : fetches information from remote into local repository
but nothing more
git merge : merges changes that were fetched
needs a source parameter
merges TO wherever HEAD is pointing to :
git merge origin/master
git pull : does both at the same time

41. Branches
Branches are separate full-blown versions of your code
Default branch = master
Which branches are there ? → git branch
Create a new branch → git branch <branchname>
Switch to branch → git checkout <branchname>
Create + switch to new branch → git checkout -b <branchname>
Show branch activity : git show-branch
Delete a branch : git branch -d <branchname>

42. Merging changes in a project
C1 C2
origin/master
C1 C2
origin/master
C3
master
master
C4 test
LICENSE : added paragraph 1
LICENSE : added paragraph 2
C1 C2
origin/master
C3 master
C4 test
LICENSE : added paragraph 1 + 2
Edited LICENSE
C5

43. Conflicting change
git merge <branchname> → conflict
git status → shows conflicted files
Resolve conflict
git commit -a → tells git conflict was resolved

44. Contributing to a Github project
Github is built on Git, so...
Clone, commit, pull, merge, push are all the same
But :
You need to fork the project first
Changes to the main repository must be requested through a
pull request

45. Creating a fork

46. Creating a fork
Will create a complete copy (not a clone) of the project
Including master, all branches, all tags, all commits, etc.
i.e. confoo/some-repo → <your_github_username>/some-repo
You can do anything in it...
But please don't if you intend to contribute back...
Which you should ofcourse ;-)

47. Next : create a branch for your feature/bugfix
Why ?
Work on multiple features/fixes at same time
Experiment without damaging your master
master should always be a fully functioning, deployable version
Name the branch well
Don't : bugfix
Do : bugfix_issue_26_fatal_error

48. Next : add/change code and commit
Don't forget unit tests, integration tests, …
Make your commit message descriptive
Don't : fixed it
Do : added real-time updates on dashboard
Each commit should contain a single feature or bugfix
→ Allows project maintainers to add small blocks of code
→ Easier than adding 50 features/bugfixes
→ Easier to test

49. Next : create a Pull Request (PR)
When you want to contribute
Partial code = OK
→ But only if you want feedback
Otherwise :
Finish your code
Make sure you have unit tests
Be descriptive in your pull request
Don't : “this will fix my issues”
Do : “Added an OAuth authentication layer”

50. Next : merging the PR
Done by a project maintainer (could be you !)
Merge from the PR branch to master
Again : have a clear merge message
→ On Github : 'Closes #56' will close Github issue and links
Congratulations, you're a Github contributor ;-)

51. Git tools
git-cola (Linux, Win, Mac)
GitHub Desktop (Win, Mac)
GitKraken (Linux, Win, Mac) - beta
Liquid prompt
Useful list :
https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools

52. Questions ?

53. Questions ?

54. Thanks !
@wimgtr
wim@cu.be