What is Git? What does it do, how does it work, how does it fit into my workflow? If you've ever wondered about the answers to any of those things, this session is designed for you, my friend. Starting with the assumption of no prior knowledge of Git or even of version control, we'll cover the technology at a theoretical level, its manifestation in your projects in the physical level, and your development workflow at the practical level - by which time you'll be ready to step out into the world, secure in your knowledge of what the heck Git is, and ready to use it in your projects - and you'll marvel at how you ever worked without it.

1. git 101: Force sensitive to Jedi Padawan

3. What is git?

4. What is ‘git’?
● Distributed Version Control System
● Git is version control for files & directories
● Runs on the command line / terminal
● Stores file versioning information
in a hidden folder at the root of the project
● Version information exists as (relatively lightweight)
difference information between files and file versions

5. Version Control
● Parallel versions
● Historical versions

6. Command Line
● Installed system-wide
● Runs on the command line
● Uses SSH Keys (with optional passwords)
● You can also use a GUI for the complex stuff

7. Everything exists locally
● Without the .git directory, it can’t work
● Everyone has a complete* copy of
the branches and history of the project
● Git is self-sufficient - no remote services needed for
branching or commits

8. Pushing & Remotes
● Unless you push your code to a remote repository,
it won’t leave your machine
● You can make peer-to-peer pushes
● It’s best to manage sharing and reduce conflicts
by pushing to a single designated remote location
● Pushing puts all of the historical and branching
information into the remote repo

9. Merges & Conflicts
● Most of the time, git can auto-merge two (or more)
changesets, because they don’t overlap
● Conflicts occur when the file data changes overlap

10. What does git give you?
● Complete version history
● Easy visualisation of changes
● Ability to work with multiple developers
and effortlessly merge changes
● Parallel versions of source code
● Ability to switch versions or roll back changes

11. Are you ready to begin?

12. Core git commands
● commit
● push
● pull
● branch
● checkout
● merge
➔ Save a change
➔ Send changes to a remote
➔ Get changes from a remote
➔ Create a new branch
➔ Switch to a branch or historical version
➔ Combine branches

13. Getting set up

14. Setting up a new git repository
Existing repository:
cd /path/to/my/repo
git remote add origin ssh://git@bitbucket.org/username/bbreponame.git
git push -u origin --all
New repository:
mkdir /path/to/your/project
cd /path/to/your/project
git init
git remote add origin ssh://git@bitbucket.org/username/bbreponame.git

15. Saving changes

16. Simple git workflow
1. Make your change(s)
2. Test it, make sure it works, and then:
git commit -am “my commit message”
git push origin master

17. git commit -am “my commit message”
git push origin master
If you don’t use -am, git will open VIM, and you
don’t want that.
your remote location name, the one you gave
it when you set up the repository,
which is usually ‘origin’
the remote branch name,
usually the name of your current
branch

18. Writing Good commit messages
A good commit message is one that:
● Has a short (<50 character) description
● Uses the imperative, present tense:
“change” not “changed” nor “changes”
● Includes motivation for the change and contrasts with
previous behavior

19. Making Good commits
● A commit message becomes your
only referral point in the projects’ history
● Your commit must represent a stable point
in your source code history - no half-baked commits!
● Only include relevant files and changes
● Treat every commit as if it were the final release

20. The GUI is your secret weapon
● A GUI (like Sourcetree) gives an
excellent overview of your
repository
● It makes it possible to craft your
commits on a line-by-line basis
● You can also modify your most
recent commit (so long as you
haven’t pushed it)

21. Synchronizing
with other repositories

22. your remote location name, the one you gave
it when you set up the repository,
which is usually ‘origin’
the remote branch name,
usually the name of your current
branch
git commit -am “my commit message”
git pull
git push origin master
if you don’t pull changes and
merge locally before pushing,
your push will likely be rejected

23. Pulling and Merging
● git fetch will retrieve version information from a remote,
but does nothing with it
● If your push is rejected, it’s likely because the remote is
more up-to-date than your local branch, and you need to
git pull those changes
● Pulling changes will automatically merge them if able;
but if it can’t, you’ll get conflicts that will need to be
resolved manually

24. Dealing with Conflict

25. Dealing with conflicts
● A conflict occurs when two changesets are trying to modify
the same lines of code
● Resolving conflicts involves manually picking which of the
two competing modifications are accepted
● Resolving a conflict doesn’t necessarily mean that the code
will still work - you’re going to have to figure that bit out
yourself and edit the file manually

26. Resolving conflicts is either:
● A yes/no selection between competing
versions of a line of code
● Or manually editing the partial
merge result to resolve the conflicts
You’re going to need a GUI

27. Avoiding Conflict
● Conflicts occur when you have an overlap, so don’t
reformat, move or refactor code when there’s a chance
someone else has also modified it
● Commit little and often
● Keep your branches up-to-date: Pull changes frequently
● Sort out your crlf settings before you start
● Some conflicts can’t be avoided

28. Branching

29. Understanding Branches
Branches:
● Are alternate versions of the working copy of your entire
project, with their own history
● Can be created from, and merged back into other branches
● Can be created explicitly, or implicitly when merging two
versions of the ‘same’ branch
● Allow you to work on features in isolation

30. Branching strategy
● master is the stable release
● development is for work in progress
● Individual features should have their own branch
● features are branched from development
● Completed features are merged in from development
● Stable development versions are merged in from master

32. Branching strategy in practice
git checkout -b development // create and switch to development
git checkout -b feature-one // create and switch to feature-one
git commit -am “my awful commit message” // create a commit on feature-one
git checkout development // switch back to development
git merge feature-one // merge feature-one into development
git checkout master // switch to master
git merge development // merge development into master
git push // push master branch to remote
git push -u origin development // push the development branch and set its
‘upstream’

33. Remote branches
● Unless you explicitly push a branch, or set an upstream for
the branch, it won’t get pushed to the remote repository

34. Useful tricks

35. Don’t use fast-forward merges
● The default behaviour of
a merge is to ‘fast
forward’ the original
when possible
● Fast-forwarding
branches doesn’t add an
extra commit for the
merge, which is cleaner
but loses some context

36. Stashing
● A ‘stash’ is a representation of the differences between your
last commit, and your current working copy.
● In order to switch branches, your current working copy
must not conflict with the branch you’re checking out.
● Been working on the wrong branch?
Stash changes. Checkout the correct branch. Apply stash.
● Got half-finished code but now you’ve got to drop
everything to fix a bug? Stash it. Come back later.

37. Git Reset
● So long as you haven’t pushed your change to a remote
repository, everything is changeable
● git reset will make it completely forget your commits
● It’s useful if you’ve made changes to the wrong branch
● It can be dangerous

38. Cherry Picking
● Merging branches brings across the entire history of both
branches and mashes them together.
● A ‘cherry pick’ takes just the changes from a single commit
and can apply them to another branch
● It’s useful, but treat it as an indication that you’ve done
something wrong if you need to use it.

39. Golden Rules

40. Golden Rules
● Commit early, commit often (when it’s stable)
● Commit only one feature and its relevant changes at a time
● Write good commit messages
● Develop on feature branches
● Merge feature branches into development,
not the other way around
● Push your changes on a regular basis

41. Remember
● Git is your time machine
● Git is your safety net

42. That’s all folks

43. Bonus

44. git push --force