git, an alternative to SVN

These are my notes from watching the git peepcode video. I highly recommend peepcode.com videos. I feel slightly guilty for publishing his notes for his screencast, which costs $9, but I hope this page will ultimately sell more of his screencasts.

“git” is source control software. For those of you who are not programmers, source control software is software that tracks changes in your files for several reasons:

  1. When collaborating on a set of files with a team of people, source control software will prevent you from overwriting somebody else’s changes to a file. You must explicitly resolve the conflicts before merging your changes into the repository.
  2. It creates a time machine of your code and allows you to literally view the state of all your files in a project at any point in time in the past. This is helpful if you unwittingly introduced a bug into your code and want to rollback to a state where the bug wasn’t there.
  3. It can be used to track different branches of development, representing different purposes or levels of stability.

Using source control software is considered to be a best-practice in software engineering. The current standard open source tool is called SVN or Subversion. Subversion is very good, and we use it in the office daily. git offers a few improvements on subversion, namely

  1. response-time / performance (very easy to work locally to make commits fast)
  2. agility (easy to make branches and makes you a faster programmer)
  3. distributed, so you can synchronize with your laptop, desktop, friend’s computer, or work computer without having to always connect to a centralized server.

You can do all of these things with SVN, but git just makes it a lot easier to. You can think of git as the “sqlite3” of version control software (source control). Not a huge deal, but if it saves me a few minutes each day, then it’s worth switching to it.

website: git.or.cz

Features of git:

  • offline: All files are committed with respect to a local repository. Therefore, git can always be used offline. No need for central server or internet.
  • distributed: can share git repository with peers—not just server.
  • agile branching: branching becomes easier than in SVN: makes you more agile
  • emphasizes content not files…. not sure how this helps me though.

INSTALLATION Mac: sudo port install git-core

Others: install from source and compile.

Latest: git clone git://git.kernel.org/pub/scm/git/git.git

CONFIGURE identify yourself to git: email and your name git config—global user.name “David Beckwith” git config—global user.email “dbitsolutions@gmail.com”

To view all users: git config—list OR cat .gitconfig

SET UP ALIASES git config—global alias.co checkout

VIEW YOUR CONFIGURATION cat .gitconfig

TO IGNORE WHITESPACE (Ruby is whitespace insensitive) git config—global apply.whitespace nowarn

Some nice aliases: gb = git branch gba = git branch -a gc = git commit -v gd = git diff | mate gl = git pull gp = git push gst = git status

START USING GIT: git init

TO IGNORE SOME FILES MAKE A FILE (in the root directory) CALLED .gitignore and add some files to it: # comments begin with hash. *.log db/schema.rb db/schema.sql

TO SCHEDULE THE ADDITION OF ALL FILES TO THE NEXT COMMIT: git add .

TO SEE WHAT THE STATUS: git status

TO COMMIT: git commit -m “First import”

TO SEE WHAT HAS BEEN COMMITTED: git ls-files

TO SCHEDULE DELETION OF A FILE: git rm

TO COMMIT ALL CHANGES IN FILES IN THE CURRENT REPOSITORY: git commit -a

TO SCHEDULE THE ADDITION OF AN INDIVIDUAL FILE TO THE NEXT COMMIT: git add

TO VIEW THE DIFFERENCE AS YOU COMMIT USE THE -v OPTION git commit -v

TO COMMIT AND TYPE THE MESSAGE ON THE COMMAND LINE USE THE -m OPTION git commit -m “This is the message describing the commit”

TO COMMIT AND GET AUTOMATICALLY ANY CHANGES FROM OTHER PEOPLE USE THE -a OPTION git commit -a

THE NORMAL COMMIT COMMAND: git commit -a -v

TO VIEW A LOG OF YOUR COMMITS git log

TO VIEW A LOG OF YOUR COMMITS WITH A GRAPH TO SHOW THE EXTENT OF THE CHANGES git log—stat

TO HAVE PAGINATION WHEN VIEWING THE LOG FILE USE THE -v OPTION git log -v

TO VISUALIZE YOUR CHANGES gitk—all

TO CREATE A NEW BRANCH: git branch

TO VIEW ALL OF THE EXISTING BRANCHES git branch

TO VIEW A LIST OF ALL BRANCHES git branch -a

TO SWITCH TO ANOTHER BRANCH. The state of your file system will change after executing this command. git checkout OR git co

TO MAKE SURE THAT YOUR NEW BRANCH GETS CHANGES FROM THE MASTER BRANCH (WHERE EVERYBODY ELSE IS WORKING) USE THE REBASE COMMAND: git rebase master

TO MERGE YOUR NEW BRANCH INTO THE MASTER BRANCH.
  1. first switch back to the master branch. git co master
  2. check to see what changes you’re about to merge together, compare the two branches: git diff master xyz
  3. if you’re in the xyz branch, and want to merge the xyz branch into it. git merge xyz

TO REVERT YOUR CHANGES to before the merge. git reset—hard ORIG_HEAD

TO RESOLVE CONFLICTS just edit your file. Remove the markings, add the file, then commit.

TO CREATE A BRANCH AND SWITCH TO THE BRANCH IN ONE MOVE: git checkout -b

TO CREATE A “CLIPBOARD” or “STASH” OF CHANGES THAT ARE NOT YET COMMITED (SO THAT YOU CAN SWITCH TO ANOTHER BRANCH IN THE MIDDLE OF YOUR CHANGES.), CREATE A STASH. git stash “Put a message here to remind you of what you’re saving to the clipboard”

TO SWITCH AWAY FROM THE CURRENT BRANCH git co
  1. do whatever
  2. switch back to the stashed branch git co

TO VIEW THE LIST OF STASHES git stash list

TO LOAD BACK THE “CLIPBOARD” OR “STASH” git stash apply
  1. now you can continue to work where you were previously.

TO DELETE A BRANCH THAT IS NOT USED ANYMORE, but already merged into the current branch. (TO CLEAN UP) git branch -d

TO DELETE AN UNMERGED BRANCH git branch -D

TO DELETE THE STASH. (ERASE THE “CLIPBOARD” FROM MEMORY) git stash clear

TO SET UP YOUR REPOSITORY FOR SHARING ON A CENTRAL SERVER
  1. Copy up your repository. e.g.: scp -r my_project deploy@yourbox.com:my_project
  2. Move your files on the remote server to /var/git/my_project
  3. For security make the owner of this project git
  4. On the repository server: sudo chown -R git:git my_project
  5. then (for security) restrict the “deploy” user to doing git-related things in /etc/passwd with a git-shell.

TO CHECK OUT THE GIT REPOSITORY TO YOUR LOCALHOST. ON YOUR LOCAL HOST do this: git clone git@yourbox.com:/var/git/my_project

TO SEE SOME INFO ABOUT THE REPOSITORY THAT WILL TELL YOU WHICH REPOSITORY IS THE MASTER AND WHICH IS THE SLAVE: cat .git/config

  1. By virtue of having cloned the remote repository, your local repository becomes the slave and will track and synchronize with the remote master branch.

TO UPDATE YOUR LOCAL BRANCH FROM THE REMOTE SERVER: git pull

TO GET A COPY OF THE ENTIRE REMOTE REPOSITORY (e.g. a repository named “laptop”) WITHOUT MERGING THEM INTO YOUR LOCAL BRANCHES USE FETCH git fetch laptop

TO MERGE TWO LOCAL BRANCHES (ie. your local xyz branch with your local master branch) USE MERGE git merge laptop/xyz
  1. this merged the (already copied laptop repository’s xyz branch) with the current branch you’re sitting in.

TO MERGE THE REMOTE BRANCH WITH YOUR LOCAL BRANCH THAT YOU ARE SITTING IN USE PULL

TO ADD LOCAL KNOWLEDGE (TO YOUR LOCAL REPOSITORY) OF A 2ND REMOTE REPOSITORY, LIKE YOUR LAPTOP git remote add laptop duo2book.local:repos/m_project
  1. “laptop” is the name of the remote repository. “duo2book.local” is the name of the machine, I guess

TO VIEW META INFORMATION ABOUT THAT REMOTE REPOSITORY git remote show laptop

TOP PUSH A COMMITTED LOCAL CHANGE OF THE xyz BRANCH TO THE REMOTE laptop BRANCH git push laptop xyz

TO CREATE A TRACKING BRANCH (A SLAVE BRANCH). Ie. to link a local branch to a remote branch: git branch—track

NOW IF YOU’RE SITTING IN THE LOCAL TRACKING BRANCH, TO PULL YOU DON’T NEED TO SPECIFY THE REMOTE TRACKING BRANCH: git pull

  1. Note: you can tracking different branches from different remote machines. For example, you can track your friend’s “upgrade” branch and track the “master” branch from your main webserver.
  1. By convention, ‘origin’ is the ‘centralized server’ which is the way SVN is usually set up on a remote server.

TO SEE WHICH LOCAL BRANCHES ARE TRACKING A REMOTE BRANCH: git remote show origin

TO WORK WITH AN SVN REPOSITORY BUT WORK WITH GIT LOCALLY: git-svn clone

  1. Now you can work with the checked out directory as though it was a git repository. (cuz it is)

TO PUSH (COMMIT) CHANGES TO THE REMOTE SERVER git-svn dcommit

TO UPDATE YOUR LOCAL REPOSITORY FROM THE SVN REPOSITORY git-svn rebase

  1. NOTE: make sure you have your perl bindings to your local svn installation.

Posted by David Beckwith on Friday, March 21, 2008