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Git tech talk


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  • 1. Git : Awesome Distributed Version Control SystemGit : Awesome Distributed Version Control SystemPresenter : Raza.Z.Sayed
  • 2. 2History● Linux kernel project● Patch emailing system● Bitkeeper from 2002 to 2005.● Why the name Git ?- “I’m an egotistical bastard, and I name all myprojects after myself.First Linux, now git.” – LinusTorvalds● First commit message : initial version of “git”,theinformation manager from hell-Linus 4/7/05
  • 3. 3Basic Concepts●Git is not like SVN (Subversion) and is fundamentally different . Git trackscontent not changes or deltas●Its like a filesystem. Its a collection of tools that implement tree history storageand directory content management system.● Non linear development, distributed development and efficient- Ruby on Rails Git repository is around 13 Mb and Subversion repository ofthe same is around 115 Mb !● Not a binary but a toolkit design in spirit of unix philosophy (Write programsthat do one thing and do it well)
  • 4. 4Basic Concepts●Git Object Database → .git directory●Git Object Types → stored in .git/objects1. Blob2. Tree3. Commit4. Tag●Git Data Model1. Git Object Types2. References (Branches and Remotes) → stored in .git/refs
  • 5. 5Basic Git Workflow● mkdir my_awesome_project● cd my_awesome_project● git init● Create a file e.g. README.txt● git status (Optional)● git add README.txt (Add to staging)● git commit -m “first commit”
  • 6. 6Basic Git Workflow● Make some changes to README.txt● Create a new file e.g. hello.rb● git status● git add hello.rb README.txt or git add . or git add --all● git commit -m “another commit”● Make changes to hello.rb● git commit -a -m “added foo method” (Wont adduntracked files to staging. git add them separately)
  • 7. 7Different ways to add● git add <list of files> (Add the list of files)● git add --all (Add all files from the project.)● git add . (Add all files from the project)● git add *.txt (Add all txt files in current dir)● git add “*.txt” (Add all txt files from the project)● git add docs/*.txt (Add all txt files from docs dir)● git add docs/ (Add all files from docs dir)
  • 8. 8Viewing changes● git diff (Show unstaged changes since lastcommit)● git diff --staged (show staged changes sincelast commit)● git log (show project history)
  • 9. 9Undo unstaged changes● git checkout . (Blow away all changes sincelast commit)● git checkout <list of files> (Blow away changesto specified files since last commit)
  • 10. 10Unstage changes● git reset HEAD (Unstage all staged files)● git reset HEAD <list of files> (Unstageparticular files) e.g. git reset HEADREADME.txt or git reset HEAD README.txthello.rb
  • 11. 11Undo commits● git reset soft HEAD^ (Undo last commit and move changesback to staging) or git reset soft HEAD~1● git reset soft HEAD^^ (Undo last two commits and movechanges back to staging) or git reset soft HEAD~2● git reset hard HEAD^ (Undo last commit and blow away allchanges) or git reset hard HEAD~1● git reset hard HEAD^^^ (Undo last three commits and blowaway all changes) or git reset hard HEAD~3● git commit --amend -m “New commit message” (Changethe last commit message)
  • 12. 12Sharing and Collaborating● Lots of different code hosting services tochoose from e.g. Unfuddle, Github, Bitbucketetc. or setup your own server.● Create a git repo on the server. This is called aremote repository.● Inside your project dir on your local machine :git remote add <some arbit name for theremote repo> <path of remote repo>
  • 13. 13Sharing and Collaborating● git remote -v (show remote repositoriesassociated with the project)● git push -u <remote repo name> <branchname> e.g. git push -u origin master● git pull (Pull changes from the remote repo)● git remote rm <remote repo name> (Delete aremote repo from the project)
  • 14. 14Sharing and Collaborating● Types of git repo urls : https://.. (Read only or readwrite depending upon permissions) , git://.. (Git readonly), git@.. (SSH read write)● git clone <remote repo url> or git clone <remote repourl> [local name]● git clone does the following three things. 1) Downloadsthe entire repo into a new directory 2) Adds originremote pointing it to clone url 3) checks out the masterbranch i.e. sets local repo HEAD to point to the masterbranch
  • 15. 15Branching● Need to work on a new feature or fix a bug thatwill take time ?. Create a new branch to work onit.● git branch <branch name> (Creates the branch)● git checkout <branch name> (Switch to thebranch)● git checkout -b <branch name> (Shortcut tocreate and switch to a branch in one step)
  • 16. 16Basic Branching Workflow● git checkout -b cool_feature● echo “This is readme for the cool feature” >README.txt● git add README.txt● git commit -m “first commit in cool_feature branch”● git checkout master● git merge cool_feature● git branch -d cool_feature (Delete the branch as weredone with it)
  • 17. 17Types of Branch Merge● Fast Forward Merge● Non Fast Forward Merge (Recursive Merge)● Recursive Merge creates an extra commitautomatically called a “Merge commit”
  • 18. 18Conflicts● Can either arise during git push or while doing amerge (merge conflict)● git push conflict scenario. Do a git pull first to fix● Two cases in which merge conflicts can arise. 1)During merging a local branch 2) Doing a git pull● git pull = git fetch+git merge. What is origin/master ?● Resolving merge conflicts
  • 19. 19Sharing local branches●A wants to create a new branch and share it.git checkout -b awesome_new_featuregit push origin awesome_new_feature●B wants to collaborate on the new branch.git pullgit checkout awesome_new_feature●Listing remote branches : git branch -r●Getting detailed information about remote branches : git remote show origin●Deleting remote branches.git push origin :awesome_new_featuregit branch -d awesome_new_feature. If this does not work then,git branch -D awesome_new_feature●Cleaning up local references to deleted remote branches : git remote prune origin
  • 20. 20Tagging● What are tags ?● Listing all tags : git tag● Creating a new tag : git tag -a v1.0 -m “version1.0”● Checkout code at a particular commit : gitcheckout v1.0● Sharing tags : git push --tags
  • 21. 21Rebase● What is a rebase and why its better than a merge ?● Dont do git pull ! . Instead do a fetch + rebase.● Remote branch rebase workflowgit fetchgit rebase● Local branch rebase workflow. e.g. To rebase branch new_feature into mastergit checkout new_featuregit rebase mastergit checkout mastergit merge new_feature
  • 22. 22Ignoring Files● Only for yourselfPut exclude patterns in .git/info/exclude file● For everyonePut exclude patterns in .gitignore file in theproject root directory● Untracking filesgit rm --cached <file name>
  • 23. 23References● Git Community Book -● Git Branching -● Git for computer scientists -● Visual Git Reference -
  • 24. 24Thank You