Configure Git and setup GitHub on new machine

configure-git.md

How to configure Git and setup GitHub on new machine

By Qin Yu, last updated in Feb 2024. I hope this will save time for everyone.

• First-Time Git Setup
  • Three config files of different levels
  • Use terminal to set identity and editor
• Connect to GitHub with SSH
• How to really commit in the past with Git for GitHub
• Reference

First-Time Git Setup

Three config files of different levels

Scope	File
system level	/etc/gitconfig
user level	~/.gitconfig or ~/.config/git/config
repository level	.git/config

Each level overrides values in the level above. You can all of your settings and where they are coming from using:

$ git config --list --show-origin

This should print nothing if git has not been used.

Use terminal to set identity and editor

1. Set identity

   $ git config --global user.name "John Doe"
   $ git config --global user.email johndoe@example.com

   If you want to override this with a different name or email address for specific projects, you can run the command without the --global option when you’re in that project.

2. Set editor Now set emacs as the default editor:

   $ git config --global core.editor emacs

   If not configured, Git uses your system’s default editor.

3. Set colour Also, enable coloured output in terminals:

   $ git config --global color.ui true

Connect to GitHub with SSH

1. Check keys to reuse

   $ ls -alhF ~/.ssh/

   if no files like ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub found then

2. Generate key pair

   $ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

3. Add key to ssh-agent

   $ eval "$(ssh-agent -s)"
   $ ssh-add ~/.ssh/id_rsa

4. Paste public key to GitHub i.e. copy the content of ~/.ssh/id_rsa.pub into GitHub -> Personal Settings -> SSH and GPG keys -> New SSH Key

5. Test

   $ ssh -T git@github.com

How to really commit in the past with Git for GitHub

The three keys are argument --date, and two environment variables GIT_AUTHOR_DATE & GIT_COMMITTER_DATE.

$ GIT_AUTHOR_DATE="2024-01-01T00:00:00" GIT_COMMITTER_DATE="2024-01-01T00:00:00" git commit --date="2024-01-01T00:00:00"

Note that the last timestamp of modification can be printed by ls -lv --time-style="+%Y-%m-%dT%H:%M:%S", I recommend you alias ll as my favourite:

$ ls -ahlv --color=auto  --group-directories-first --time-style="+%Y-%m-%dT%H:%M:%S"
total 4220
...
drwxr-sr-x   8 qyu hpc-088    4096 2024-02-01T18:51:03  datasets
drwx------   6 qyu hpc-088    4096 2024-02-05T20:24:59  downloads
drwxr-sr-x   2 qyu hpc-088    4096 2022-05-03T22:31:54  environments
...

Reference

• 1.6 Getting Started - First-Time Git Setup
• Generating a new SSH key and adding it to the ssh-agent
• Testing your SSH connection

Thanks for this, very useful - worked first time for me!

Works fantastic, thanks for your work! 😄

On the point, thanks!