Git Intro

A git introduction for the "Sviluppo Applicazioni Software" class (2014) Computer Science Turin University

Transcript

1. Collaborative Development using SAS 2013/14 Alessandro Baldo
2. Version Control “ The management of changes to documents, computer programs, large web sites, and other collections of information ” — Wikipedia
3. Version Control “ The management of changes to documents, computer programs, large web sites, and other collections of information ” — Wikipedia
4. Manual version control MyProject MyProject.old MyProject.bak MyProject.last MyProject.coolIdea MyProject.from-John MyProject-6/5/14 MyProject-2 One does not simply find the right “version”
5. Version Control - Why? • Powerful “Ctrl + Z” • Backup • Collaboration
6. Git “ Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency ”
7. Git - Download http://git-scm.com/download/ Linux > apt-get install git Mac OSX > brew install git > > apt-get install git > brew install git
8. Git - Setup Basic git config > git config --global user.name "Jonh Doe" > git config --global user.email "johndoe@unito.it" > git config --global color.ui true > git config --global core.editor vim
9. Git - Setup SSH identity your RSA public key is in id_rsa.pub > ssh-keygen > ls ~/.ssh/ id_rsa id_rsa.pub known_hosts
10. Git - Basic concepts Repository = where the magic happens transform a directory in a Git repository clone a remote repository > git init [dir] > git clone <repository> [dir]
11. Git - Basic concepts Working directory = where the hard work it’s done! > git status show the status of the files from git’s perspective Changes not staged for commit: modified: README.txt Untracked files: hello.java
12. Git - File lifecycle untracked modified unmodified staged Tracked new file git add git add git commit edit file
13. Git - Basic concepts To start tracking a new file or stage a modified file in the working directory to stage all the files in the working directory > git add [file] … [file] > git add .
14. Git - Basic concepts To commit the staged changes then edit the commit message in your editor! shortcut > git commit > git commit -m “commit message”
15. Git - Basic concepts What is a commit? “ a commit is a full snapshot of the contents of your working directory (everything being tracked by git, anyway), and it's kept track of using a unique 40 character SHA1 hash. This way, the exact state of your project can be referred to, copied, or restored at any time.” Pragmatic definition “a small and cohesive set of changes annotated with a message”
16. Git - Commit history Git maintains the history of commits shows this history Tips • git log --help for more options • You can use a GUI to view the log (gitk or other GUI tools) > git log
17. Git - Commit history commit 3cbb6aae5c0cbd711c098e113ae436801371c95e Author: Jonh Doe <jdoe@gmail.com> Date: Fri Jun 4 12:58:53 2010 +0200 fixed readme title differently commit 3ac015da8ade34d4c7ebeffa2053fcac33fb495b Author: Jonh Doe <jdoe@gmail.com> Date: Fri Jun 4 12:58:36 2010 +0200 fixed readme title :
18. Git - Navigate history To navigate commit history restore the working directory at a particular revision (PIT recovery) To go back at where we started > git checkout <revision> > git checkout master
19. Git - Local operations Working directory Staging Area Repository Stage Commit Checkout a revision
20. Git - “change” the history What if I want to make changes starting from an old commit?
21. Git - “change” the history What if I want to make changes starting from an old commit? The commit history is a tree
22. Git - Branching Starting from a this linear history we can do some interesting stuff C1 C2 C4 C3 HEAD master C1 C2 C4 C3 HEAD master
23. > git checkout c2 -b coolStuff > [edit something] > git commit -a -m “Hello branch!” Git - Branching C1 C2 C4 C3 HEAD master C5 coolStuff
24. > git branch master *coolStuff Git - Branching Show available branches > git checkout <branch> Move between branches
25. > git checkout master > git merge coolStuff Updating 8bd6d8b..8f7c949 Fast-forward more.txt | 1 - 1 files changed, 0 Git - Branching C1 C2 C4 C3 HEAD master C5 coolStuff C6 No conflicts in this case => fast forward git create a new commit!
26. Git - Branching If auto-merge fails we need to manually resolve conflicts lists files interested by conflicts We can manually edit the files or use a diff tool (k3diff, vimdiff, etc.) with git mergetool > git status
27. Git - Branching Git presents conflicts with the syntax: > cat README.md <<<<<<< HEAD Many Hello World Examples ======= Hello World Lang Examples >>>>>>> coolStuff Once we are satisfied with the merge we need to commit the changes
28. Git - Other commands • git help • git <command> --help • git reset HEAD • git revert • git commit --amend • git tag • git stash • git diff “Oh dear! Oh dear! I shall be too late!”
29. Git - Remote operations • No collaboration • No backup
30. Distributed Version Control
31. Distributed Version Control Centralized Distributed Server Repository Clients
32. Git - Remote operations We can clone a remote repository We can add a remote repository > git clone git://remote_repo/repo.git > git remote add staging git://git. kernel.org/staging.git
33. Git - Remote operations We can retrieve changes from a remote branch and then we can merge back in the local branch > git fetch origin master > git merge origin/master
34. Git - Remote operations Shortcut > git pull
35. Git - Remote operations We can push changes to a remote branch if the remote branch doesn’t exist it will be created Tip: git push to push to the default tracked branch > git push <remote> <branch>
36. Git - Remote operations Good Practices • always pull before start working • double-check your local commit before a push • you can push multiple commit at once
37. Git - Branching model Git allows great flexibility in branching/merging strategies flexibility = complexity
38. Git - Branching model
39. Git - Branching model One simple yet powerful model (simplify from nvie.com ) Master Dev Feature branch (eg. new login form)
40. Git - Collaboration • Collaborative coding using git it’s possible but not always easy • Git does not solve coordination issue between humans
41. Git - Collaboration
42. Git - Pull request model • Fork a repository • Make changes • Push them to your copy • Make a pull request • Discuss the pull request
43. More infos • Git docs git-scm.com/documentation • Pro Git by Scott Chacon (Apress) git-scm.com/book • Interactive Cheatsheet ndpsoftware.com/git-cheatsheet.html • Git interactive tutorial pcottle.github.io/learnGitBranching • Successful branching model nvie.com/posts/a-successful-git- branching-model
44. Any Question?
45. This work is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/4.0/ Author Alessandro Baldo speakerdeck.com/baldoalessandro/git-intro Thanks to Mattia Bertorello