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Sat 17 August 2013

Git is a version control system (VCS).

Note: For some reason the ass clowns at Github quietly put in support for large files, so you have to install an extension to github. If you don't, it can be painful to work with github from the command line.

For OSX:

brew install git-lfs

Git Cheat Sheet

Command Example Definition
Init git init Start a repository
Clone git clone git://somewhere.com/something.git [new_name] Create a copy of a repository
Remote git remote -v Display remote repository
Push git push origin [master] Share changes to an upstream remote (origin) for a branch
Commit git commit -m 'update' One step add/push upstream
Add git add *.c Add files to the repository or to stage files for commit
Fetch git fetch [origin] Pull all changes from a remote repository that have been pushed since you cloned it. Note this doesn't merge any of the changes.
Pull git pull Will automatically fetch and merge changes from upstream into current branch
Tag git tag -a v1.4 -m 'my Version 1.4' Create an annotated tag, note you may have to: git push origin v1.4 or git push origin --tags to get tags push on upstream server.
Status git status Reports the status of untracked changes in your working repository
Diff git diff Display changes between working directory and repository
Rm git rm file.c Remove files from repository
Mv git mv from_file to_file Move files
Log git log View the commit log

Git Setup

Let's start off with making git look nice:

git config --global color.ui true

Since we will work remotely, we need to tell git who we are. Git stores that info in ~/.gitconfig

git config --global user.name "walchko"
git config --global user.email kevin.walchko@hotmail.com

Working with Git

You may need to create an ssh keys following the github directions


  1. create a key:

    ssh-keygen -t rsa -C "pi@bender.local"
  2. Add the key to the key agent:

    pi@bender ~ $ eval "$(ssh-agent -s)"
    Agent pid 12480
    pi@bender ~ $ ssh-add ~/.ssh/id_rsa
    Identity added: /home/pi/.ssh/id_rsa (/home/pi/.ssh/id_rsa)

    You can also run ssh-add -l to see what keys have been loaded.

  3. Go to github and add a new ssh key under your profile. Copy/paste in the key (use more ~/.ssh/id_rsa.pub) making sure not to add or remove white space. You can also use pbcopy < ~/.ssh/id_rsa.pub to copy it to your clip board on macOS.

  4. Then try to ssh in:

    pi@bender ~ $ ssh -T git@github.com
    The authenticity of host 'github.com (' can't be established.
    RSA key fingerprint is 1d:57:ac:a4:76:23:2d:34:63:1b:56:4d:74:7f:76:48.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added 'github.com,' (RSA) to the list of known hosts.
    Hi walchko! You've successfully authenticated, but GitHub does not provide shell access.


Now clone a repository, make sure you use the ssh address and not the default https one

git clone git@github.com:walchko/soccer.git

Note: The https one has https in the address: https://github.com/walchko/soccer2.git

if you accidentally clone the https one, you can switch to ssh by

git remote set-url origin git@github.com:walchko/soccer2.git

Git Workflow

Read this awesome guide

  1. Make sure your current copy is up to date

    git pull
  2. Create a new branch to hold your new feature

    git checkout -b my-cool-new-thing
  3. Edit your code. To see status:

    git status
    On branch master
    Your branch is up-to-date with 'origin/master'.
    Changes not staged for commit:
      (use "git add <file>..." to update what will be committed)
      (use "git checkout -- <file>..." to discard changes in working directory)
            modified:   docs/computers/git.rst
    no changes added to commit (use "git add" and/or "git commit -a")
  4. Add files to stash (AKA index or cache):

    git add *
  5. Commit files (locally) to HEAD in your .git repository:

    git commit -m "what did you do?"
    pi@bender ~/soccer/IMU $ git push origin master
    Counting objects: 12, done.
    Compressing objects: 100% (8/8), done.
    Writing objects: 100% (8/8), 736 bytes, done.
    Total 8 (delta 6), reused 0 (delta 0)
    To git@github.com:walchko/soccer.git
       8162ade..cd9a476  master -> master
  6. Push changes upstream to github (or where ever) so everyone can use them

    git push origin master

    or git push because origin master is the default.

  7. Create a tag

    git tag -a v0.5.3 -m "update"
    git push origin v0.5.3

To undo what you have committed already and basically create an anti-patch for each commit

git revert 0766c053 25eee4ca a867b4af


Sometimes you need to include another git in your project ... how do you do that?

git submodule add git@github.com:adafruit/Adafruit_Python_PureIO.git

This will include it. Now you can track development and update as necessary to the latest code. This will also add a .gitmodules to your project which will track what submodules (other git projects) you are tracking.

When you need to clone your project (and the submodules too) though, you now have to do:

git clone --recursive git@github.com:...

This will pull your project and any submodules your project has too.

Setting up your own server on the RPi


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