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Introduction to Git and Github

Introduction to Git and Github

Introduction to Git and Github - An introductory presentation to Git and Github along with basic concepts.

Senthilkumar Gopal

August 23, 2013

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  1. Who is this for? • Folks starting to use Git

    or foraying just now • Folks who are using SmartGit :) • Using Git as CVCS http://rogerdudler.github.io/git-guide/
  2. Why command line No Installation Simple to use Comes bundled

    with Git as Git-Bash Consistent across OS
  3. A simple workflow Clone or create new repository Update/Add files

    Stage the changes Review the changes Commit the changes
  4. Git Setup $ git config --global user.name "John Doe" $

    git config --global user.email [email protected] $ git config --global color.ui true
  5. Create a new Repository $ cd project/ $ git init

    # initializes the repository $ git add . # add those 'unknown' files - ADDS FOR STAGE $ git commit # commit all changes, edit changelog entry - M $ git rm --cached <file>... # ridiculously complicated command to undo, in case you forgot .gitignore $ git reset HEAD <file> # same as before $ git init project002 #shortcut for mkdir project002 && cd project002 && git init
  6. Git Clone $ git clone git://github.com/sengopal/simplegit.git Initialized empty Git repository

    in /private/tmp/simplegit/.git/ remote: Counting objects: 100, done. remote: Compressing objects: 100% (86/86), done. remote: Total 100 (delta 35), reused 0 (delta 0) Receiving objects: 100% (100/100), 9.51 KiB, done. Resolving deltas: 100% (35/35), done. $ cd simplegit/ $ ls copy the entire history of that project so you have it locally
  7. Git status $ git status # On branch master #

    # Initial commit # # Changes to be committed: # (use "git rm --cached <file>..." to unstage) # # new file: README # new file: hello.py # # Changed but not updated: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: README #
  8. Git add Start tracking new files and also to stage

    changes to already tracked files $ touch README.md; echo “test” > README.md $ git status $ git add . $ git status $ git diff Shortcut: git commit -a # the -a flag pulls in all modified files will commit all changed files (but not new files, those need to be added to the index with git-add). If you want to commit only certain files then you will need to stage them first with git-add
  9. Git diff To compare two revisions of a file, or

    your current file and a previous revision $ git diff README.md $ git diff --staged README.md $ git diff HEAD README.md $ git diff --stat README.md To compare 2 revisions of a file: $ git diff <commit1> <commit2> <file_name>
  10. .gitignore $ git add .gitignore will use its rules when

    looking at files to commit to ignore from staging $ git rm --cached filename will not ignore a file that was already tracked before a rule was added to this file # to remove the tracked file - Caution: This deletes the file $ git config --global core.excludesfile ~/.gitignore_global file can be committed into the repository, thus sharing the rule list with any other users that clone the repository.
  11. Git Commit $ git commit -m 'my awesome changes' -m

    option not given - open a text editor for you to write your commit message. $ git commit -a automatically stage all tracked, modified files before the commit
  12. Git push remote branches are identical to local branches except

    that Git will not allow you to check them out. However, you can merge from them, diff them to other branches, run history logs on them, etc. You do all of that stuff locally after you synchronize. $ git push <remote> <branch> # push new commits to the <branch> on the <remote> repository For someone coming from CVS, the commit to the central repository now requires two steps. $ git clone # creates a remote called origin for push and fetch
  13. $ git pull <remote> <branch> # fetches code and merges

    it $ git fetch <remote> <branch> # fetches code without merging $ git pull --tag <remote> <branch> # pulls tags as well Git pull and fetch
  14. Git reset just a plain old git reset should unstage

    accidental git add $ git reset --soft undo the last commit and put the files back onto the stage $ git reset --hard undo the last commit, unstage files AND undo any changes in the working dir $ git-reset --hard <hash> Revert to a previous commit by hash $ git-reset --hard HEAD^ your last commit before pull/merge
  15. Git reset $ git reset HEAD <file> unstage file and

    copy from latest commit $ git reset -- <file> unstages specific files and copy files from the stage $ git checkout HEAD -- files copies files from the latest commit to both the stage and the working directory. $ git checkout -- files copies files from the stage to the working directory. Use this to throw away local changes.
  16. git branch The default branch in a git repository is

    called master. $ git branch <branch-name> To create a new branch use $ git branch To see a list of all branches in the current repository type $ git checkout <branch-name> If you want to switch to another branch you can use $ git checkout -b <branch-name> To create a new branch and switch to it in one step $ git branch -d <branch-name> # To delete a branch $ git stash branch <branch-name> # To create a branch with current changes
  17. git rebase $ git checkout experiment $ git rebase master

    First, rewinding head to replay your work on top of it... Applying: added staged command $ git rebase -i $ git rebase --interactive
  18. git merge If you want to merge a branch (e.g.

    master to release), make sure your current branch is the target branch you'd like to merge into (use git branch or git status to see your current branch). $ git merge experiment where experiment is the name of the branch you want to merge with the current branch $ git diff to see pending conflicts you have to resolve. $ git checkout -b linux-work # create a new branch $ <make changes> $ git commit -a $ git checkout master # go back to master branch $ git merge linux-work # merge changesets from linux-work
  19. git merge $ git checkout master $ git rebase topic

    First, rewinding head to replay your work on top of it... Fast-forwarded master to topic. This command lays the latest changes to topic right on top of the master branch, and preserves all of your commit history- laying them right on the end of the master branch’s commit history. $ git merge --squash topic This command will result in a commit log like a normal merge- meaning that all of the individual commit messages from the topic branch will become one single “merge” message.
  20. mergetool $ cat /usr/local/bin/extMerge #!/bin/sh /Applications/p4merge.app/Contents/MacOS/p4merge $* $ git config

    --global merge.tool extMerge $ git config --global mergetool.extMerge.cmd 'extMerge "$BASE" "$LOCAL" "$REMOTE" "$MERGED"' $ git config --global mergetool.trustExitCode = false ~/.gitconfig [merge] tool = extMerge [mergetool "extMerge"] cmd = extMerge "$BASE" "$LOCAL" "$REMOTE" "$MERGED" trustExitCode = false
  21. gitconfig $ git config --global core.editor emacs $ git config

    --global core.pager '' $ git config --global color.ui true $ git config --global diff.external extDiff $ git config --global core.whitespace \ trailing-space,space-before-tab,indent-with-non-tab $ git config --global merge.stat true
  22. git remote $ git remote add origin user@server:/path/to/project.git adding a

    remote branch $ git remote -v origin [email protected]:github/git-reference.git (fetch) origin [email protected]:github/git-reference.git (push) list the remotes available $ git remote rm origin removing an existing remote alias
  23. Quick tips $ git log -- filename see the history

    of revisions to a file $ gitk inspect history visually, shows you how the revisions are connected $ git log this pipes a log of the current branch into your PAGER $ git log -p # same as above, but append a patch after each commit message $ git show HEAD show commit info, diffstat and patch of the tip of current branch
  24. Quick tips $ git filter-branch --tree-filter 'rm -f filename' HEAD

    remove all instances of a file from every commit $ git filter-branch --env-filter \ "export [email protected]" HEAD change your email in all commits $ git blame <file-name> history of user changes in a file $ git log --pretty=oneline --graph pretty log with a graph of changes done