Deep Thought

Git

4 min read

Git

Reasons to use version control

  • Have a record of what, when and why you did something
  • Snapshots of different development states
  • Compare different versions of files
  • Easily share work with others
  • Integrate changes from others (merging)
  • Mark finished product versions (tags)
  • Try out new ideas (branches)
  • Best practice and Industry standard

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Glossary

  • Repository
    • Stores complete history, branches, tags (and other meta-information)
  • Working Copy
    • Your “playground”, actual source code
  • Commit / Revision
    • A specific, single version/snapshot
  • Branch
    • A distinct line of development

Distributed Version Control

  • Every user has a full copy of the repository
  • Repositories can be synchronized (push/fetch)
  • Off-line access

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Git

  • Started in 2005 by Linus Torvalds
  • Used for Linux Kernel development
  • Highly distributed
  • Cryptographic integrity

Install & Setup

git config --global user.name 'Norbert Winkler'
git config --global user.email 'n.winkler@htlkrems.at'

Cheat Sheet

https://education.github.com/git-cheat-sheet-education.pdf

Creating Repositories

  • Create a new local repository
$ cd path/to/project
$ git init
# or
$ git init new_dir
$ cd new_dir

Adding files

  • Adding new files
  • Current state of the file is recorded
# add a new file foo.txt with contents 'bar'
$ >foo.txt echo 'bar'
git add foo.txt

Writing history

$ git commit -m "Showcased how to add files to git"

Updating Files

  • Tell Git about new changes
  • Same thing as adding new files (Git only cares about the content of files)
# add new content to foo.txt
$ >>foo.txt echo 'new content'
$ git add foo.txt
$ git commit -m 'updated file'

Browsing history

$ git log
commit 87bebde3c4c24c34f8b61d3332ac18df416d28c7
Author: norwin <me@norwin.at>
Date:   Tue Jun 11 04:35:35 2024 +0200
 
    Updated file
 
commit f49e31ed76c07887481bea4ba4dffd606b794c45
Author: norwin <me@norwin.at>
Date:   Tue Jun 11 04:32:13 2024 +0200
 
    Showcased how to add files to git

Working copy status

  • Shows list of modified, new and staged files
  • Also reminds you of important commands
$ git status
On branch main
nothing to commit (working directory clean)

Inspecting changes

  • Show current changes
  • Show differences between commits
  • Show differences between branches
$ git diff
$ git diff HEAD~ HEAD
$ git diff branch1 branch2

What the fork?

  • Try out new features
  • In an ideal world: one branch per feature
  • Branches are cheap, use them often
  • Branches can be deleted
# create and switch to new branch
$ git branch newbranch
$ git checkout newbranch
 
# list branches (star marks active branch)
$ git branch
main
* newbranch

Merging changes

  • Integrate changes from a branch
  • Integrate changes from others
# Checkout the branch you want the changes to merge into
$ git checkout main
# merge changes from other branch
$ git merge newbranch

Merge conflicts

  • Merges don’t always go well
  • Git inserts conflict markers into conflicting files
  • git status tells you the current state
  • Remove conflicts and add that state of the file with git add
$ git diff
diff --cc foo.txt
…
<<<<<<< HEAD
current content
=======
branch content
>>>>>>> newbranch
 
# manually resolve conflict
$ vim foo.txt
 
# add new state to git
$ git add foo
$ git commit

Stash

  • Temporarily put aside changes
  • Handy for urgent bugfixes
# stash changes
git stash save
 
# Your working copy is reset to your last commit
# You can checkout another branch and come back later
 
# recall changes from stash
git stash pop

Forking existing projects

  • Get a copy of the repository
  • fetch + merge to update your copy
$ git clone https://github.com/git/git.git git
$ cd git
# ...
$ git fetch
$ git merge origin/branch

Syncing changes

  • Fetch downloads the latest changes from the remote repository
  • With merge you can merge these changes with your local branch
  • pull is a shortcut for fetch + merge
  • push uploads your local changes to the remote repository
$ git pull
# make changes and commit them ...
# afterwards:
$ git push

Ignoring Files

  • You don’t want all files to be versioned

    • Temporary files
    • Build artifacts
    • Configuration, especially Passwords !!

  • Create a .gitignore file in your projects’s root folder

  • https://git-scm.com/docs/gitignore

git add .gitignore
git commit -m "added .gitignore"

Sample .gitignore

## Get latest from `dotnet new gitignore`

# User-specific files
*.rsuser
*.suo
*.user

# Build results
[Dd]ebug/
[Rr]elease/
[Bb]in/
[Oo]bj/

# Visual Studio 2015/2017 cache/options directory
.vs/

# Click-Once directory
publish/

# JetBrains Rider
*.sln.iml
.idea/

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