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Intro to Git presentation. Presented in ATLRUG in 2008.

Jesse Newland

October 02, 2011

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  1. What is Git? • A popular distributed version control system

    designed to handle very large projects with speed and efficiency. • http://git.or.cz/
  2. For the brave # install gnupg, gettext $ curl -O

    http://kernel.org/pub/software/scm/git/ git- $ tar xzf git- $ ./configure $ make $ sudo make install $ curl http://www.kernel.org/pub/software/scm/git/git- manpages-1.5.4.tar.bz2 $ sudo tar xjf git-manpages-1.5.4.tar.bz2 -C /usr/ local/share/man
  3. For the weak sudo port install git-core +svn sudo apt-get

    install git-core sudo yum install git-core
  4. Initial Setup $ git config --global user.name='My Name' $ git

    config --global [email protected] # optional, for pretty colors $ git config --global color.diff=auto $ git config --global color.diff.new=cyan $ git config --global color.diff.old=magenta $ git config --global color.diff.frag=yellow $ git config --global color.diff.meta=green $ git config --global color.diff.commit=normal
  5. Why Git? • Distributed, not Centralized • Revolutionizes how you

    use branching • Extremely stupidly ridiculously fast, even with large projects • Community
  6. Distributed VCS • Every Git working directory is a full-fledged

    repository with full revision tracking capabilities, not dependent on network access or a central server. • Commits happen offline. • Commits can then be pushed and pulled between repositories with shared history.
  7. quick survey #2 • How many of you use branching?

    • Work exclusively on trunk/master? • NEVER work on trunk/master?
  8. Why branching with Git is awesome • Instant $ time

    git checkout -b newbranch Switched to a new branch "newbranch" real 0m0.227s • Private • Merging doesn’t suck
  9. • Prototype well-developed changes • Commit early and often •

    Review and revise before you merge Topic Branches
  10. Offline Operations • Performing a diff • Viewing file history

    • Committing changes • Merging branches • Obtaining any other revision of a file • Switching branches
  11. Online operations are fast too $ time git clone --depth

    1 git://github.com/josh/ rails.git ... real 0m9.088s
  12. This looks familiar $ git status $ git log $

    git blame $ git add FILE $ git rm FILE $ git mv FILE $ svn status $ svn log $ svn blame $ git add FILE $ git rm FILE $ git mv FILE
  13. git status • Untracked Files • Brand new file •

    Changed but not updated • Locally changed file not in the index • Changes to be committed • ‘The Index’
  14. The Index • Staging area for your next commit •

    Sort of like files marked A, M, D in svn status output
  15. One major difference • After making any changes to the

    working directory, and before running the commit command, you must use the add command to add any new or modified files to the index.
  16. Example # create bar and to the index echo “foo”

    > bar git add bar # change bar, and thus remove from the index echo “ “ >> bar # add bar to the index again git add bar
  17. Committing • git commit • commit what’s in the index

    • git commit -a • adds changed but not untracked files to the index, then commits • exactly like SVN
  18. Diffs # diff between working tree and the index $

    git diff # diff between the index and last commit $ git diff --cached # diff between working tree and last commit $ git diff HEAD
  19. Logs # just like svn $ git log # find

    a commit changed a specific string $ git log -S"def stupid_method" # log with patches for each commit $ git log -p
  20. git revert != svn revert # most similar to svn

    revert $ git checkout . # reverse commit <rev> and commit the result $ git revert <rev>
  21. Branching # create a new branch $ git branch NEW_BRANCH

    # switch to this branch $ git checkout NEW_BRANCH # create a new branch and check it out in one step $ git checkout -b NEW_BRANCH
  22. More Branching # view available branches $ git branch *

    new_branch master # delete a branch $ git branch -d ALREADY_MERGED_BRANCH $ git branch -D BAD_BRANCH
  23. Diffing and Logging with Branches # log of changes to

    other_branch not in master $ git log NEW_BRANCH..master # diff of those changes $ git diff NEW_BRANCH..master
  24. Merging # get back to the master $ git checkout

    master # merge in changes from your other branch $ git merge NEW_BRANCH # optionally, delete the branch $ git branch -d NEW_BRANCH
  25. Rebasing # store local changes not in BRANCH_NAME as patches,

    updates the local branch to BRANCH_NAME, then applies the patches $ git rebase BRANCH_NAME
  26. Danger, Will Robinson • Rebase is dangerous • Rewrites commit

    history • Don’t use on a branch you’re sharing
  27. Easy Conflict Resolution $ git merge conflict_branch Auto-merged README CONFLICT

    (content): Merge conflict in README Automatic merge failed; fix conflicts and then commit the result. # fix conflict then commit $ vim README $ git add README $ git commit -m “fixed merge conflict”
  28. Common Use Cases • Contributor • Create Patches • Send

    Patches • Maintainer • Review Patches • Apply Patches
  29. Track the upstream # add a remote $ git remote

    add jnewland git://github.com/ jnewland/atlrug-demo.git # add a branch $ git checkout -b jnewland/master # update the tracking branch $ git pull jnewland master
  30. Merge it all together # switch back to the master

    $ git checkout master # update master with your changes $ git merge my_branch # update master with upstream changes $ git merge jnewland/master
  31. Grab mtodd’s changes # add a remote $ git remote

    add mtodd git://github.com/mtodd/ atlrug-demo.git # add a branch $ git checkout -b mtodd/master # pull the changes $ git pull mtodd master
  32. Merge, then push! # switch back to master $ git

    checkout master # merge $ git merge mtodd/master # push $ git push
  33. “the best part about GIT is that no one has

    to know you’re using it”
  34. basic git-svn workflow $ git svn clone REPO_URL # ...

    hack hack hack ... $ git commit -a # ... hack hack hack ... $ git commit -a $ git svn rebase $ git svn dcommit
  35. better workflow $ git svn clone REPO_URL $ git checkout

    -b new_branch # ... hack hack hack ... $ git commit -a $ git svn rebase $ git svn dcommit $ git checkout master $ git branch -d new_branch $ git svn rebase