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 2025. 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
• References

First-Time Git Setup

Three config files of different levels

Git uses three configuration levels, each overriding the previous one:

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

To view all active settings and where they are coming from:

git config --list --show-origin

This should print nothing if git has not been used.

Use terminal to set identity and editor

1. Set Git name and email

   git config --global user.name "John Doe"
   git config --global user.email "[email protected]"

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

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

   git config --global core.editor emacs

   If not configured, Git defaults to your system 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 List existing SSH keys:

   ls -alhF ~/.ssh/

   If no files like ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub are found, then:

2. Generate key pair

   ssh-keygen -t rsa -b 4096 -C "[email protected]"

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 connection

   ssh -T [email protected]

How to really commit in the past with Git for GitHub

The three keys are the argument --date and two environment variables: GIT_AUTHOR_DATE and 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"

You can view the last modification timestamp using:

ls -lv --time-style="+%Y-%m-%dT%H:%M:%S"

I recommend my favourite alias for ll:

$ alias ll='ls -ahlv --color=auto --group-directories-first --time-style="+%Y-%m-%dT%H:%M:%S"'
$ ll

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
...

To avoid pasting three times, I added another alias to ~/.bashrc:

alias gitpast='f(){ GIT_AUTHOR_DATE="$1" GIT_COMMITTER_DATE="$1" git commit --date="$1"; }; f'

Then, I can commit in the past with a single command:

gitpast "2024-01-01T00:00:00"

References

• 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!

Thank you so much !!

Maybe at the step 3, it would be useful to specify that it it is only needed if your key has a passphrase.

Maybe at the step 3, it would be useful to specify that it it is only needed if your key has a passphrase.

Thanks for your feedback! But let's not change it: even if your key doesn't have a passphrase, adding it to ssh-agent allows the agent to manage multiple keys and automatically provide the correct one when needed. Am I right?