Git tech talk

Git tech talk

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  Git : AwesomeDistributed Version Control SystemGit : Awesome Distributed Version Control System Presenter : Raza.Z.Sayed
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  2 History ● Linux kernelproject ● Patch emailing system ● Bitkeeper from 2002 to 2005. ● Why the name Git ? - “I’m an egotistical bastard, and I name all my projects after myself.First Linux, now git.” – Linus Torvalds ● First commit message : 'initial version of “git”,the information manager from hell'-Linus 4/7/05
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  3 Basic Concepts ● Git isnot like SVN (Subversion) and is fundamentally different . Git tracks content not changes or deltas ● Its like a filesystem. Its a collection of tools that implement tree history storage and directory content management system. ● Non linear development, distributed development and efficient - Ruby on Rails Git repository is around 13 Mb and Subversion repository of the same is around 115 Mb ! ● Not a binary but a toolkit design in spirit of unix philosophy (Write programs that do one thing and do it well)
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  4 Basic Concepts ● Git ObjectDatabase → .git directory ● Git Object Types → stored in .git/objects 1. Blob 2. Tree 3. Commit 4. Tag ● Git Data Model 1. Git Object Types 2. References (Branches and Remotes) → stored in .git/refs
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  5 Basic 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”
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  6 Basic 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 add untracked files to staging. git add them separately)
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  7 Different ways toadd ● 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)
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  8 Viewing changes ● gitdiff (Show unstaged changes since last commit) ● git diff --staged (show staged changes since last commit) ● git log (show project history)
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  9 Undo unstaged changes ●git checkout . (Blow away all changes since last commit) ● git checkout <list of files> (Blow away changes to specified files since last commit)
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  10 Unstage changes ● gitreset HEAD (Unstage all staged files) ● git reset HEAD <list of files> (Unstage particular files) e.g. git reset HEAD README.txt or git reset HEAD README.txt hello.rb
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  11 Undo commits ● gitreset soft HEAD^ (Undo last commit and move changes back to staging) or git reset soft HEAD~1 ● git reset soft HEAD^^ (Undo last two commits and move changes back to staging) or git reset soft HEAD~2 ● git reset hard HEAD^ (Undo last commit and blow away all changes) or git reset hard HEAD~1 ● git reset hard HEAD^^^ (Undo last three commits and blow away all changes) or git reset hard HEAD~3 ● git commit --amend -m “New commit message” (Change the last commit message)
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  12 Sharing and Collaborating ●Lots of different code hosting services to choose from e.g. Unfuddle, Github, Bitbucket etc. or setup your own server. ● Create a git repo on the server. This is called a remote repository. ● Inside your project dir on your local machine : git remote add <some arbit name for the remote repo> <path of remote repo>
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  13 Sharing and Collaborating ●git remote -v (show remote repositories associated with the project) ● git push -u <remote repo name> <branch name> e.g. git push -u origin master ● git pull (Pull changes from the remote repo) ● git remote rm <remote repo name> (Delete a remote repo from the project)
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  14 Sharing and Collaborating ●Types of git repo urls : https://.. (Read only or read write depending upon permissions) , git://.. (Git read only), git@.. (SSH read write) ● git clone <remote repo url> or git clone <remote repo url> [local name] ● git clone does the following three things. 1) Downloads the entire repo into a new directory 2) Adds origin remote pointing it to clone url 3) checks out the master branch i.e. sets local repo HEAD to point to the master branch
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  15 Branching ● Need towork on a new feature or fix a bug that will take time ?. Create a new branch to work on it. ● git branch <branch name> (Creates the branch) ● git checkout <branch name> (Switch to the branch) ● git checkout -b <branch name> (Shortcut to create and switch to a branch in one step)
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  16 Basic 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 were done with it)
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  17 Types of BranchMerge ● Fast Forward Merge ● Non Fast Forward Merge (Recursive Merge) ● Recursive Merge creates an extra commit automatically called a “Merge commit”
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  18 Conflicts ● Can eitherarise during git push or while doing a merge (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
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  19 Sharing local branches ● Awants to create a new branch and share it. git checkout -b awesome_new_feature git push origin awesome_new_feature ● B wants to collaborate on the new branch. git pull git 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_feature git 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
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  20 Tagging ● What aretags ? ● Listing all tags : git tag ● Creating a new tag : git tag -a v1.0 -m “version 1.0” ● Checkout code at a particular commit : git checkout v1.0 ● Sharing tags : git push --tags
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  21 Rebase ● What isa rebase and why its better than a merge ? ● Dont do git pull ! . Instead do a fetch + rebase. ● Remote branch rebase workflow git fetch git rebase ● Local branch rebase workflow. e.g. To rebase branch new_feature into master git checkout new_feature git rebase master git checkout master git merge new_feature
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  22 Ignoring Files ● Onlyfor yourself Put exclude patterns in .git/info/exclude file ● For everyone Put exclude patterns in .gitignore file in the project root directory ● Untracking files git rm --cached <file name>
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  23 References ● Git CommunityBook - http://git-scm.com/book ● Git Branching - http://pcottle.github.com/learnGitBranching/ ● Git for computer scientists - http://eagain.net/articles/git-for-computer-scientists/ ● Visual Git Reference - http://marklodato.github.com/visual-git-guide/index-
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  24 Thank You