EBC Exercise 16 git

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thumb‎ Embedded Linux Class by Mark A. Yoder

git is a distributed revision control system with an emphasis on being fast. It was initially designed and developed by Linus Torvalds for Linux kernel development. The purpose of this lab is to get hands on experience with git to learn how it works and how to use it.

Much of the material here has come from Pro Git. We'll be using github to practice gitting.

Here's an O'Reilly Webcast: Git in One Hour

0. Set Up Git

If you haven't done so already, go to EBC_Exercise_05_Getting_Exercise_Support_Materials#Set_Up_Git and follow the directions for setting up git.

1. Play with git locally

Pro Git has a nice on-line book with lots of good details. I'll lead you through many parts of it. The first chapter is Getting Started. Here are the topics:

1.1 - About Version Control
1.2 - A Short History of Git
1.3 - Git Basics
1.4 - Installing Git
1.5 - First-Time Git Setup
1.6 - Getting Help
1.7 - Summary

I'll cover Git Basics in class and you have already done parts 1.5 and 1.6 to set up for github. I suggest you take a look at Getting Help and then move on.

2. Git Basics

Chapter is on Git Basics. The topics are:

2.1 - Getting a Git Repository
2.2 - Recording Changes to the Repository
2.3 - Viewing the Commit History
2.4 - Undoing Things
2.5 - Working with Remotes
2.6 - Tagging
2.7 - Tips and Tricks
2.8 - Summary

There is lots of good material here. I suggest you work through it all. Section 2.1 shows how to clone a remote repository.

Questions you should be able to answer after doing chapter 2

  1. How do you stage a file?
  2. How do you view staged and unstaged changes?
  3. How do you view comment history?
  4. You've just committed something and realize you meant to have committed one more file. How do you add that file to the commit you just did?
  5. How do you unstage a file?
  6. How do you unmodify a file?
  7. After running the remote -v how do you tell if a site is read only or read/write?
  8. What's the difference between a lightweight and an annotated tag?

3. Git Branching

Chapter 3 is on branching. Here's the topics from the book:

3.1 - What a Branch Is
3.2 - Basic Branching and Merging
3.3 - Branch Management
3.4 - Branching Workflows
3.5 - Remote Branches
3.6 - Rebasing
3.7 - Summary

I'll work through 3.1 in class. Read through 3.2 and then do the following exercise.

Merging helloWorld.py

  • clone my repository (The pass phrase is Hiapp)
bone$ git clone git@github.com:MarkAYoder/gitLearn.git
bone$ cd gitLearn
  • Edit helloWorld.py and add a print with your name on it.
  • Compile to be sure it works.
  • Stage and commit helloWorld.py. You may have to merge. Keep everyone else's name in the file.
  • Push it to the repository.

Once everyone has done this we should have a file with everyone's name in it.

Merge Tools

There are a few cool tools to help with merging, notably a graphical diff tool. Many such tools are available and will easily hook up to Git such as kdiff3, meld, vimdiff, etc. (more are listed in ProGit section 1.5). For this example, we're going to use meld.

You can set up your diff tool by navigating to your .git repository and running:

host$ sudo apt update
host$ sudo apt install meld
host$ git config --global diff.tool meld

You can also get rid of the annoying confirmation message by running:

host$ git config difftool.prompt false

You can then diff a file in meld using (and background it so you can keep using your shell):

host$ git difftool [filename] &

Leaving the filename blank should open all files that have been modified.

Lastly, because that command feels really long (and because this class is all about learning how to use Linux more effectively), we're going to add an alias to our .bashrc (or .zshrc, or other .*rc file, depending on what shell you use) file to shorten this.

In terminal open up your .bashrc file with your favorite text editor:

host$ nano ~/.bashrc

This file will have a bunch of stuff that configures your shell, but you're looking for the area that has aliases in it. Add the following lines below the last set of aliases:

# alias for Git
alias gdiff='git difftool &'

This adds gstat and gdiff as commands in bash, so you can type a single command to show the git status or the diff of all modified files in your favorite diff viewer.

Checking out a remote branch

Suppose the remote repo has a branch called summer2021 that you want to make local and have the local copy track the upstream copy

bone$ git fetch origin summer2021:summer2021
bone$ git checkout summer2021
bone$ git push --set-upstream origin summer2021

Moving from svn

Here's a nice article on a common git workflow for those who are moving from svn.

thumb‎ Embedded Linux Class by Mark A. Yoder