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http://j.mp/psumac9
Part I - Git Basics
What is Version Control?
Why use it?
What is Git?
Git versus Subversion
Git Overview
What is Version Control?
Management of changes to documents like source code, scripts, text files
Provides the ability to check documents in and out of a repository
Version Control System (VCS)
Source Code Management (SCM)
What is Version Control?
"Version control is a system that records changes to a file or set of files over time so that you can recall specific versions later.” ( git-scm.com )
Why Use it?
You can revert and go back easily
Removes risk of updating your code
See process of steps you have taken
Fantastic tool that encourages collaboration
Why Use it?
Easy testing on multiple systems
Runs on Windows, Mac, and Linux!
Reuse of old code
Ability to go back in time! See how far you've come
Easy sharing and collaboration
What can I Use Git For?
ANY text based file
binary files too, but not as efficiently
Python, Bash, Perl, Ruby, scripts, text, config files, etc.
List is shorter of what you can’t use it for!
Git versus SubversionLightning fast! Checkouts are MUCH faster
Distributed versus centralized
No need for constant network access
Merging is much easier
Easier to ignore files and edit other properties
Git easily handles renaming and moving files
Git Overview
Git is distributed
You checkout and you have the full repo
Changes are applied locally first
Backups are everywhere!
Each member of your team has a local copy!
TerminologyRepository
Working Directory
Staging Area
Used for preparing commits
Git Directory
Repository object store/Remote Repository
Final destination for you data changes
Terminology
Working Directory
Index/ Staging
Directory/Repository
Local Local
Remote
Local
Git File ClassificationsTracked
Already in the repo
Ignored
Can exist but git ignores (specified in .gitignore)
Untracked
What's not tracked or ignored
Git File StatesModified
Changed but not yet committed
Staged
Modified filed marked to go into next commit
Committed
Safely stored in the repo
Git File States Lifecycle
Basic Git workflow
Working Directory
Staging Area
Repository
Example Workflow
git init
git add .
git commit -m “Added project files.”
git push
How Git Works
git init repo git add.
Creates .git folder in current
directory
1 2 3 git commit -m " "
Files committed to
local repo, ready to be
push to remote
git push (origin
master)
Files are pushed to repository
(final destination)
Add all files to be committed
Git Data IntegrityGit Checksums Everything!
Git uses SHA1 hash on all tracked files
It knows if anything has changed
Git excels at tracking renamed or moved files too
Resist modifying files when renaming or moving them
What about SHA1 hash collisions?
Git Help
Online docs are really, really good
http://git-scm.com
Command line help
git help
git help <conmand>
How to Install
git-scm.com/downloads
OS X: Terminal.app, Windows: Git Bash
Update to latest version
git clone https://github.com/git/git
Embedded with many Git GUI client apps
How to Configure
$ git config
Contains items such as name, email, editor, diff tool
How to Configure$ git config
Located in 3 places
/etc/gitconfig -- Values for all users
~/.gitconfig -- Values for single user
.git/config -- Value for single repository
$ git config --list
Configure Line EndingsEnd of line characters differ based on client OS
Windows uses two invisible characters
CR (Carriage Return)
LF (Line Feed)
OS X and Linux use one invisible character
LF (Line Feed)
Embrace the native line endings for each OS to be HAPPY
Line Ending Modescore.autocrlf true
Recommended for cross platform projects from Windows clients
core.autocrlf input
Recommended for cross platform projects from OS X / Linux / Unix clients
core.autocrlf false
Recommended only for single platform projects
Line Endings on Windows
Enable auto convert to LF on Windows by using git config to set core.autocrlf to true:
Line Endings on OS X
On OS X, enable auto convert CRLF to LF:
Creating Repositories
git init ProjectName.git
Initializes a new and clean repository in new directory
git clone <repoURL> <directory>
The process of copying an existing Git repository locally to your computer
Copies the entire repository history and file revisions
Ignoring Files
Git ignore files, paths specified in the .gitignore file
Specifies files/folders that are not tracked via Git
Wildcards
*NotForRepo*, *.dmg, etc.
10.9.4-Lab-Image.dmg
LargeDataFile-NotForRepo.db
Status of File ChangesHow do I know what has changed?
$ git status
Status reports different states
Untracked
Modified
Staged
DifferencesCommits are all about what is … different!
Viewing the differences
At the command line
$ git diff FileName
In GUI Apps
Kaleidoscope, FileMerge, Changes.app, etc.
Staging Files
Added files are staged
Why not just directly commit the changes?
git add -v <file/folder_name>
git add -v .
git add -A
Unstaging Files
File not yet tracked but staged:
$ git rm --cached NewFile.txt
Files already tracked in repo, revert to previous
$ git reset HEAD FileName.txt
Committing ChangesThis process saves the revisions made to the repository
Commit often - You will thank yourself later!
Or else! Larger changes are much harder to pick apart and revert back to.
Each commit should encapsulate a single fix*
git commit -m <commit_message>
What's the most important part of the above command?
Pushing to Remote Repos
Local versus Remote (Hosted) Repos
Commit changes to local repo first, then push all to remote repo(s)
Cloning from a remote host
Branching from a remote/local host
Read/Write versus Read-Only Accounts
Accessing Remote ReposNetwork Based
HTTPS
SSH
Git Protocol (daemon)
Multiple Remotes
Fetch updates
Pruning Local Branches
Viewing Changes
Logs
$ git log --shows all pulls + info about each
Git LogUsed for git reset
Git Log
List changes made in a commit
git log
View entire change log
$ git log -p -2
Lists changes in last two commit entries
Reverting Changesgit reset
Change back to file state at specific commit
git revert
Creates a new commit and undoes last changes
git checkout <commit> -- <filename>
Changes branch you’re currently working on
Hands On Git DemoCommand Line
Install
Configure
Create new repo
Add to .gitignore
Add files
Commit changes
Add remote
Push Items
Revert Items
Clone Existing Repo
GUI Clients
SourceTree (OS X and Windows)
GitHub (OS X and Windows)
Tower (OS X)
http://git-scm.com/downloads/guis
Diff GUI Applications
FileMerge
Changes.app
Kaleidoscope is totally AWESOME!
SourceTree In Depth DemoInstall
Configure
.gitignore
Create New Repo
Adding Items
Commit Items
Push Items
Revert Items
Clone Existing Repo
SourceTree In Depth DemoBookmarks List
Recommended Git Defaults
Line Endings
Host Repositories Feature
Working Directory, Branches, Searching
Excellent Git Flow Integration
Kaleidoscope Demo
Using Kaleidoscope for diffs, conflicts, merges
Excellent support for Git and SourceTree
Part II - Advanced GitFetching
Tags
Branches
Merging
Origin (Remotes)
HEAD Reference
Pushing to Remotes
Automate Authentication
Advanced Git Ignores
Stashing
Advanced Diffs
Searching
Moving Files
Bisect
Pull Requests
Fetching
Get updates from remote repo
Does not apply changes to local working directory
Useful to run before doing a pull
$ git fetch origin
TagsUseful for marking a specific commit
Example: Mark commit that is for major version change
1.0.1
1.0.2
Useful for regression testing with the ‘git bisect’ command
Tags
Create a tag syntax
$ git tag <commit hash ID>
Branches
“master” branch is the default
Helps to separate lines of development
Ex: Master, Hotfix, Development, Feature, Release
Merging of branches is where Git excels
“Git Flow” is a popular branching model
BranchesCreate and switch to new branch
$ git checkout -b <branch>
Checkout (switch to) branch
$ git checkout master
Delete branch
$ git branch -d <branch>
Deleting Branches
Delete Remote Branch
$ git push origin —delete <branchname>
Don’t forget to delete all stale remote-tracking branches!
$ git remote prune origin
Otherwise your local repo will still show it
Merging Changes
Demo of the merge process
Conflicts
Cherry Picking
Show how to change diff tool to GUI app
Merging Changes
Use FileMerge for merging conflicts
$ git mergetool -t opendiff
Remotes
Default is called "origin" (leave it this name)
Versus Local Repo
Multiple
Primary, off site, etc.
Be careful that local branches still track the primary repo branch after adding more remotes
Automate Authentication
SSH Remote Host
Create Open SSH Key pair, place id_rsa.pub key on remote host
HTTPS
Credential Helpers for command line
SourceTree and other GUI apps manage this well
Adding a Remote Repo
$ git remote add origin ssh://user@host/path/to/repo.git
HEAD Reference
HEAD is a reference to branch or a specific commit
What does "detached HEAD" mean, and why should I care?
Working directory state points to specific commit and not latest commit on a branch
Pushing Changes
git push origin master
Pushes all your commits on master branch to the origin remote
Push to other locations
git push
Advanced Git IgnoresGlobal Git Ignore File in ~/.gitignore
Git tracks files, not directories
By default, Git does not track empty directories
Add Empty Dir to RepoCreate a .gitignore file in the directory to ignore
Ignore all files except the .gitignore file
Stashing ChangesVery useful for when you’re not ready to commit the changes to the repo yet
Saves your changes to the local Git repo and does not commit them
Stash the changes (makes working directory clean)
$ git stash
Restore the changes
$ git stash pop
Advanced Diffs
Logging Changes of one file
Tags
git diff <tag1> <tag2>
Branches
git diff branch1..branch2
Searching
Search file names, commit messages
$ git log -S<string>
RegEx for commit messages
$ git log -G”RegEx Pattern Here”
Who Made Changes?
List who modified what files
git blame -l FileName.txt
git blame -l —show-email FileName.txt
Moving Files Demo
Git excels at moving files
When moving or renaming files do NOT modify them for most efficient commit
Recall that everything is checksummed, Git knows if a file is the same one regardless if the name changed
Hunting For Bugs
Git provides a very handy function to help find which commit introduced a bug
You tell Git what commit point was good and bad
$ git bisect start
$ git bisect bad # Current version is bad
$ git bisect good v2.6.13-rc2
Advanced Demo
Detached HEAD
Configure Remote
Push Changes to remote
Moving Files, Stashing
Branching
Merging, Tagging
Diffs
Searching
GitFlow
Bisect
Repo Hosting ServicesGitHub, BitBucket, Google Code
CodeSpaces, SourceRepo
Assembla, Gitorious
GitLab
Git.psu.edu for Penn Staters
Lots more!
Self-Hosted Repos
SSH
Atlassian Stash
Enterprise GitHub
GitLab
Git FlowWorkflow for managing branches
Five different branch types
Feature
Develop
Release
Hotfixes
Master
Removing Tracked Files
$ git rm —cached <FileName>
Update repo .gitignore to ignore the file(s)
Removing Untracked Files
$ git status
$ git clean -n
Dry run, shows what would be deleted
$ git clean -f
Removes the files listed in previous command
Tips and Tricks
Aliases
Can be used to shorten commands
Pros and Cons on shared systems
Auto-Completion
Auto completes Git commands; like Linux
Best Practices
Handling Very Large Repos
run `git gc` every 100 or so commits
http://blogs.atlassian.com/2014/05/handle-big-repositories-git/
Simple solution is a shallow clone
git clone --depth depth remote-url
What's New in Git 2.0
Default push changes
Simple versus matching
git push (with no arguments) defaults to simple push mechanics
git add now includes removals to the repo
Pre 2.0 only added new or modified files
Lessons Learned
Write good commits messages!
Really helps when writing release notes
Easy to search
Helps future self!
Lessons Learned
Take the time to write good commit messages when they are fresh in your mind
There will be a time when you need to search your commit messages and it will really help you out.
Be nice to your future self
“Where / when / how did I fix that issue?”
Lessons LearnedSubmodules and dependencies
Branch Names
No White Space Permitted (tabs, spaces)
Supports Hierarchical Names*
‘bug/pr-1023’, ‘bug/pr-17’
$ git show-branch ‘bug/*’
Lessons Learned
Tags
Use "annotated" most of the time
Working with others
Team collaboration tips
Lessons LearnedStart small
Pick one project to implement Git
Use just the develop and master branches at first, add additional branches as you get more comfortable
Watch commits on GitHub, fork a project, create pull requests
Lessons Learned
Using a VCS/SCM makes you more mobile and code tested on more environments makes that project more robust.
Commenting helps to clarify your comments, design flow, and for code review
Further Reading
Cherry Picking
Patches
Reflog
Rebasing
ResourcesGit Docs
http://git-scm.com/documentation
Git cheat sheets
Lynda.com (lynda.psu.edu)
Git Essential Training, GitHub for Web Designers
Fundamentals of Software Version Control
Resources
Atlassian Git Tutorials
https://www.atlassian.com/git/tutorial
https://try.github.io
O'Reilley Books
“McCullough and Berglund on Mastering Git”
Thank You!
Please submit Session Feedback!
http://j.mp/psumac9
