Working with GIT

Working with GIT - presented at ONF Member Workdays
By Brian O'Connor, ON.Lab

Transcript

1. Brian O'Connor Open Networking Lab 2/11/2015 Working with
2. What this talk will cover Git Basics - Getting started - Basic workflow and commands GitHub - Getting started - Anatomy of a project - How to contribute
3. Disclaimer This will be a bit of a whirlwind tour, and I will borrow some of the materials from git-scm.com and github.com There are plenty of in-depth (and better) tutorials and videos that get into a lot of the details that I may gloss over.
4. Why Version Control? • For Version History ◦ Allows you to go back and revert changes and recover or compare against old version ◦ Makes experimentation easier (using branches) • To Facilitate Collaboration ◦ Allows you to make modifications to files in parallel as a team and merge the result
5. What is Git? vs. CVS, Subversion, Perforce Git, Mercurial, Bazaar
6. How do I start? • A brand new project ◦ git init # in the project's top level directory • An existing project (more common) ◦ git clone [URL] ◦ git clone https://github.com/mininet/mininet.git Note: Projects will contain a .git directory that will track will contain all changes and metadata. Also, if you don't have git installed, do this first: https://help.github.com/articles/set-up-git/
7. Branching • master ◦ default branch when you check out a project ◦ usually "stable" and "deployable" • topic branches ◦ best practice for changes ◦ local only, unless you push them somewhere git checkout -b my-feature master # to create git checkout master # to switch branches
8. Committing Changes 1. Make a change to a file 2. Look at what's changed (optional) ◦ git status 3. Stage your files for commit ◦ git add [file name] 4. Commit! ◦ git commit # opens the default editor Shortcut: git commit -a -m"Commit Message"
9. Anatomy of a commit commit ea9ae214f9bca97537378f205910d62b7aa4be47 tree de130618eaf06592df72b43b06e88ea87160d8b6 parent 0cc189e6814cb0bf5af049fd6074212a2599a571 Author: Brian O'Connor <bocon@onlab.us> Date: Fri Feb 6 16:41:49 2015 -0800 Using CommandSession console instead of System.* in AbstractShellCommand print and error fixes ONOS-986 diff --git a/cli/src/main/java/org/onosproject/cli/AbstractShellCommand.java b/cli/src/main/java/org/onosproject/cli/AbstractShellCommand.java index e6a62d0..b404db6 100644 --- a/cli/src/main/java/org/onosproject/cli/AbstractShellCommand.java +++ b/cli/src/main/java/org/onosproject/cli/AbstractShellCommand.java @@ -62,7 +62,7 @@ public abstract class AbstractShellCommand extends OsgiCommandSupport { * @param args arguments */ public void print(String format, Object... args) { - System.out.println(String.format(format, args)); + session.getConsole().println(String.format(format, args)); } /** commit hash (SHA1) author information commit message commit diff git show [commit hash | branch | HEAD]
10. Looking at the past git log [branch | commit hash] git log --oneline --graph --decorate=short * 0094997 (tag: 2.2.0b3) fixing install-mininet-vm.sh * 7a411b6 Merge pull request #453 from cdburkard/master |\ | * c2341cd update examples README with new examples |/ * 4219b22 (tag: 2.2.0b2) 2.2.0b2 * 08ab7e8 Merge pull request #452 from mininet/nat-cmd |\ | * ab97dfa (origin/nat-cmd, nat-cmd) fixing no --nat issue | * af1ccf9 Updating NAT class to use gateway interface * | 3ef6bcf Additional info about --nat and LinuxRouter |/ * 015cd9e Merge pull request #443 from cdburkard/devel/cluster |\ | * bbf94cd use rcmd instead of quietRun when shutting down remote nodes * | 3d44bcd MiniNet -> Mininet * | 1817cbc Pass pyflakes * | e0bf8ec Minor code cleanup
11. : the social network for code
12. Getting Started on GitHub • Create an Account • Add your public key (strongly recommended) ◦ makes pushing changes easier Get started @ https://github.com/
13. Anatomy of a project page repository viewer commit log project forks issue tracker pending contributions project wiki download URL
14. Pulling the latest changes • git clone [URL] ◦ create a new repository with the latest code • git pull [remote] [branch] ◦ gets the latest code for the specified branch on the remote and merges it into your current local branch • git fetch [remote] ◦ updates your local metadata with the latest information about the remote repository
15. Dealing with merge conflicts • Happens when two people change the same file in a conflicting way ◦ Usually manifest themselves when you do git pull • What you'll see ◦ CONFLICT (modify/delete): ... # Automatic merge failed; fix conflicts and then commit the result. • How to fix it ◦ Update the offending file(s) ◦ Stage the changes using git add [filename] ◦ Commit using git commit
16. Forking a project • Your own copy of someone else's project • Somewhere to push your local changes ◦ And collaborate with others on them, too! • Push your changes to GitHub ◦ git push origin [branch name] • To fork, click the "Fork" button on the upstream project page in GitHub ◦ Creates a clone of the upstream in GitHub
17. Keeping your fork up to date • Set up remote ◦ git remote add upstream [upstream URL] 1. Fetch the latest from the remote ◦ git fetch upstream 2. Checkout your local master ◦ git checkout master 3. Merge the upstream changes ◦ git merge upstream/master 4. Push the changes to GitHub ◦ git push origin master
18. Pull requests • Push the latest changes to your topic branch to GitHub ◦ git push origin [branch] • Click the "Compare & pull request" button on your fork's project page:
19. Issue tracking and GitHub wiki • Automatically built-in • Issue tracker ◦ Useful for reporting bugs, tracking new features, etc. ◦ Automatically integrated using commit messages e.g. "Closes #843" • Wiki ◦ Great place to put project documentation e.g. installation instructions, tutorials, etc. ◦ Editable by anyone with a GitHub account ◦ Versioned
20. Live Demo • Fork a project • Make a change and commit • Pull and Merge conflicts • Push to remote • Create a pull request
21. Other Topics • .gitignore file ◦ Tells git to ignore certain files or patterns, like build artifacts • git stash ◦ Useful for quickly stashing local changes while pulling/updating code • git rebase ◦ Replay your branch from a new parent ◦ NEVER rebase code that's been pushed* ◦ Used heavily in Gerrit workflow
22. Merge vs. Rebase Note: NEVER rebase public (i.e. pushed to remote) branches Exception: Okay to rebase pending changes/commits in Gerrit Images from: https://www.atlassian.com/git/tutorials/merging-vs-rebasing/workflow-walkthrough git merge master git rebase master Feature Branch
23. Resources Cheat Sheet https://training.github.com/kit/downloads/github-git-cheat-sheet.pdf Collection of Tutorials https://help.github.com/articles/good-resources-for-learning-git-and- github/ Fantastic (free!) eBook http://git-scm.com/book/en/v2 Tons more easily found via Google