GIT FOR SYSTEM ADMINS JUSTIN ELLIOTT PENN STATE UNIVERSITY 1 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 versioning system • Version Control System (VCS) • Source Code Management (SCM) 2 WHY SHOULD YOU USE IT? • Enables you to easily back out of mistakes • Removes the risk of updating your scripts and code • Excellent for collaboration with others • Greatly enhances your ability to be agile and move quickly with scripts and coding. 3 GIT VERSUS SUBVERSION • Lightning fast! Checkouts are MUCH faster • Clients have the full repo • Distributed versus centralized • No need for constant network access • Easier to ignore files and edit other properties • Git easily handles renaming and moving files • Branching and Merging is much easier in Git 4 GIT: A GREAT SCM TOOL • Extremely fast performance • Excellent data integrity • Git checksums everything (SHA-1) • Easy to learn and start small 5 GIT OVERVIEW • Git is distributed • All clients have the full repo • Changes are applied to local repo first • Backups are everywhere • Each member of your team has a local copy 6 GIT TERMINOLOGY • Repository • Working Directory • Staging Area • Remote 7 GIT FILE CLASSIFICATIONS • Tracked • Already in the repo, Git is watching it • Ignored • Can exist locally, not in repo and git ignores it • Untracked • What's not tracked or ignored 8 GIT FILE STATES • Modified • Is tracked, changed but not yet committed • Staged • Modified filed marked to go into next commit • Committed • Safely stored in the repo 9 BASIC GIT WORKFLOW Working Directory Staging Area Repository 10 HOW TO INSTALL GIT • Download from http://git-scm.com/ downloads • OS X: Terminal.app • Windows: Git Bash • Embedded with many Git GUI client apps 11 CONFIGURING GIT • $ git config • Contains items such as name, email, editor, diff tool 12 CONFIGURE LINE ENDINGS • End of line characters differ based on client OS • OS X and Linux use one invisible character • LF (Line Feed) • Windows uses two invisible characters • CR (Carriage Return) + LF (Line Feed) • Embrace the native line endings for each OS 13 LINE ENDING MODES • core.autocrlf true • Use for cross platform projects on Windows clients • core.autocrlf input • Use for cross platform projects on OS X clients • core.autocrlf false • Use only on single platform projects 14 LINE ENDINGS ON OS X Enable auto convert CRLF to LF: 15 LINE ENDINGS ON WINDOWS Enable auto convert to LF on Windows by using git config to set core.autocrlf to true: 16 CREATE A REPOSITORY • $ 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 17 STATUS OF FILE CHANGES • How do I know what has changed? • $ git status • Status reports different states • Untracked • Modified • Staged 18 IGNORING FILES • Some files should never reside in the repo • The .gitignore file solves this • Specify file names, directory paths to ignore • Supports Wildcards *NotForRepo*, *.dmg 10.9.4-Lab-Image.dmg LargeDataFile-NotForRepo.db 19 ADDING FILES THE REPO • Adding files are “staged” • Why not just directly commit the changes? • git add -v <file/folder_name> • git add -v . • git add -A 20 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 21 COMMITTING CHANGES • This 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> 22 VIEWING DIFFS • Commits are all about what is different • Viewing the differences • $ git diff <FileName> • GUI Apps • Kaleidoscope, FileMerge, Changes.app, etc. 23 VIEWING COMMIT LOGS • $ git log • $ git log -p -2 • Lists changes in last two commit entries 24 BRANCHES • “master” is the default branch • Merging of branches is where Git excels • Help to separate lines of development • “Git Flow” is a popular branching model • Ex: Master, Hotfix, Development, Feature, Release 25 BRANCHES • $ git checkout master • Create and switch to new branch • $ git checkout -b <branch> • Delete branch • $ git branch -d <branch> 26 HEAD REFERENCE • HEAD is a reference to latest commit in branch OR a specific commit • What does "detached HEAD" mean, and why should I care? • Occurs when you check out a specific commit in a branch versus the latest commit of branch 27 COMMAND LINE DEMO • Create Repo • Review Logs • Create .gitignore • View Diffs • Add Files • Checkout commit • Commit Changes 28 REMOTE REPOS • Local repo on your client only • Remote is a Git host to push to • You clone from remotes 29 REMOTE REPOS • Network Based • SSH • HTTPS • Git Protocol (daemon) 30 SELF-HOSTED REPOS • SSH • Enable SSH, create “bare” repository on server • Atlassian Stash • Enterprise GitHub • GitLab 31 REMOTE REPOS • 3rd Party • GitHub, BitBucket, Google Code • CodeSpaces, SourceRepo • Assembla, Gitorious • git.psu.edu (For Penn Staters) • And possibly more, I’m sure… 32 CLONING A REPOSITORY • The process of copying an existing Git repository to your computer • A cloned repo includes the entire file history changes and commit messages • Git clone command example: • $ git clone https://server.edu/RepoName.git 33 PUSHING CHANGES • $ git push origin master • Push (upload) the ‘master’ branch to the ‘origin’ remote host 34 GUI CLIENTS • http://git-scm.com/downloads/guis • GitHub (OS X and Windows) • SourceTree (OS X and Windows) • Tower (OS X) 35 BASICS OF GITHUB DEMO • Create Repo • Commit • Create .gitignore • View Diffs • Add Files • Review Logs 36 SOURCETREE • Integrated support for Git hosting services • GitHub, BitBucket, Kiln, Stash • Helps to simplify more complex tasks • Decent UI 37 SOURCETREE DEMO • Create repo • Review Logs • Create .gitignore • View Diffs • Add files • Create Branch • Commit changes • Merge Branch 38 LESSONS LEARNED • Start small • Pick just one project to manage with Git • Use remotes when ready • GitHub, BitBucket, SSH host 39 LESSONS LEARNED • Take the time to write good commit messages • 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?” 40 GIT COMMAND LINE HELP • $ git help • $ git help <command> 41 RESOURCES AND TRAINING • Official Git Site • http://git-scm.com • Git Cheat Sheets • Git Pro Book 42 RESOURCES AND TRAINING • http://try.github.com • http://atlassian.com/git • O’Reilly • “McCullough and Berglund on Mastering Git” 43 Q & A Justin Elliott jelliott [at] psu.edu ! @justindelliott 44 THANK YOU. Justin Elliott jelliott [at] psu.edu ! @justindelliott 45.