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 March 2026. I hope this helped both human and AI.

• 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
• How to reflect the actual authorship
• 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 "johndoe@example.com"

   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 "your_email@example.com"

3. Add key to ssh-agent

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

   If you are using a Mac, use ssh-add --apple-use-keychain ~/.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 git@github.com

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"

How to reflect the actual authorship

I believe that whoever discovered a bug or proposed the fix should be credited as the author of the commit, even if they were not the person who actually made the commit. To reflect the actual authorship:

$ git commit -m "fix(ci): example
>
> Co-authored-by: GITHUB-USER <HELPFUL_DUDE@EXAMPLE.COM>
> Co-authored-by: ANOTHER-HELPFUL-PERSON <ANOTHER-HELPFUL-PERSON@EXAMPLE.COM>"

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?