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[https://en.wikipedia.org/wiki/Git_(software) Git] is the version control system (VCS) designed and developed by Linus Torvalds, the creator of the Linux kernel. Git is used to maintain NixOS packages, as well as many other projects, including sources for the Linux kernel.  
[https://en.wikipedia.org/wiki/Git_(software) Git] is the version control system (VCS) developed by Junio C Hamano and designed by Linus Torvalds (Creator of the Linux kernel). Git is used to maintain NixOS packages, as well as many other projects, including sources for the Linux kernel.  


== Installation ==
== Installing and configuring Git ==


Install the <code>git</code> package.  
On NixOS, Git can be installed and configured at either the system level or the user level with [[Home Manager]].


=== Additional features ===
=== System-wide installation ===


Install <code>tk</code> to use the git gui:
Git can be installed system-wide either by adding it to the list of system environment packages:
 
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
  environment.systemPackages = with pkgs; [
    git
  ];
</nowiki>}}
 
Or by enabling the NixOS Git module:
 
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
  programs.git.enable = true;
</nowiki>}}
 
Additional Git module configuration options can be found at {{nixos:option|programs.git}}.
 
{{note|Configuration options provided by this module are applied at the system level and therefore apply to all users on the system.}}
 
=== User-level configuration with Home Manager ===
 
Git can be configured using [[Home Manager]]:
 
<syntaxhighlight lang="nix">
  programs.git = {
    enable = true;
    settings.user = {
        name  = "John Doe";
        email = "johndoe@example.com";
    };
  };
</syntaxhighlight>
 
Aliases can be added with:
 
<syntaxhighlight lang="nix">
  programs.git = {
    enable = true;
    settings.alias = {
      ci = "commit";
      co = "checkout";
      s = "status";
    };
  };
</syntaxhighlight>
 
Git [https://git-lfs.com/ LFS] can be enabled with:
 
<syntaxhighlight lang="nix">
  programs.git = {
    enable = true;
    lfs.enable = true;
  };
</syntaxhighlight>
Configure git-credential-helper with libsecret:
 
<syntaxhighlight lang="nix">{ pkgs, ... }:
 
{
  programs.git = {
    enable = true;
    package = pkgs.git.override { withLibsecret = true; };
    settings = {
      credential.helper = "libsecret";
    };
  };
}</syntaxhighlight>
 
To add additional configuration you can specify options in an attribute set, so to add something like this:
 
<syntaxhighlight lang="ini">
[push]
        autoSetupRemote = true
</syntaxhighlight>
 
To your <code>~/.config/git/config</code>, you can add the below to <code>settings</code>
 
<syntaxhighlight lang="nix">
{ pkgs, ... }:


<syntaxhighlight>
{
git citool
  programs.git = {
    enable = true;
    settings = {
      push = { autoSetupRemote = true; };
    };
  };
}
</syntaxhighlight>
</syntaxhighlight>


== Configuration ==
==== Using your public SSH key as a signing key ====


Git can be configured using [[Home Manager]]:
To configure git to automatically sign your commits using your public SSH key like so:


<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
{
   programs.git = {
   programs.git = {
     enable = true;
     enable = true;
     userName  = "John Doe";
     signing = {
     userEmail = "johndoe@example.com";
      key = "ssh-ed25519 AAAAAAAAAAAA...AA username@hostname";
      signByDefault = true;
     };
    settings = {
      gpg = {
        format = "ssh";
      };
    };
   };
   };
}
</syntaxhighlight>
</syntaxhighlight>


== Management of the <code>nixpkgs</code> git repository ==
However, note that this will also require Home Manager to manage your SSH configuration:
 
<syntaxhighlight lang="nix">{   
  programs.ssh = {
    enable = true;
    addKeysToAgent = "yes";
  };
}</syntaxhighlight>
 
=== Enabling Git UI ===
 
Install <code>tk</code> to use the git gui:
 
<syntaxhighlight lang=console>
$ git citool
</syntaxhighlight>
 
Or you may wish to install the <code>gitFull</code> package, which includes <code>git gui</code>, <code>gitk</code>, etc. This can be installed either through system environment packages or by setting the package module option:


<code>nixpkgs</code> has become a git repository of quite substantial size with > 160 000 commits (as of early 2019). This brings many unoptimized tools to their limits, leading to long waiting times on certain operations. Here we’ll collect useful info on how to manage that.
<syntaxhighlight lang="nix">
  programs.git = {
    enable = true;
    package = pkgs.gitFull;
  };
</syntaxhighlight>


=== git ===
== Management of the <code>nixpkgs</code> git repository ==


git itself might not perform as usual with the default settings
<code>nixpkgs</code> has become a git repository of quite substantial size with > 889 000 commits (as of late 2025). This brings many unoptimized tools to their limits, leading to long waiting times on certain operations. Here we’ll collect useful info on how to manage that.


==== <code>git-gc</code> ====
=== Garbage collecting ===


Normal <code>git gc</code> should work as usual, but you should force a full garbage collect every half a year or so. <code>git gc --aggressive</code> is the command for that. For the author it did not work on the first try, since their laptop’s memory was too small and it went out of memory. According to [https://stackoverflow.com/a/4829883/1382925|this StackOverflow] answer it suffices to set some local repository config variables.
Normal <code>git gc</code> should work as usual, but you should force a full garbage collect every half a year or so. <code>git gc --aggressive</code> is the command for that. For the author it did not work on the first try, since their laptop’s memory was too small and it went out of memory. According to [https://stackoverflow.com/a/4829883/1382925|this StackOverflow] answer it suffices to set some local repository config variables.


git config pack.windowMemory 2g
<syntaxhighlight lang=console>
git config pack.packSizeLimit 1g
$ git config pack.windowMemory 2g
$ git config pack.packSizeLimit 1g
</syntaxhighlight>


worked well on a machine with about 6–8 GB of free RAM and two processor threads, and reduced the size of the <code>nixpkgs</code> checkout from ~1.3 GB to ~0.95 GB.
worked well on a machine with about 6–8 GB of free RAM and two processor threads, and reduced the size of the <code>nixpkgs</code> checkout from ~1.3 GB to ~0.95 GB.
= Serve Git repos via SSH =
This section implements [https://git-scm.com/book/en/v2/Git-on-the-Server-Setting-Up-the-Server Git on the Server - Setting Up the Server] on NixOS.
See also: [[gitolite]].
== Configuration ==
<syntaxhighlight lang="nix">
{ config, pkgs, ... }: {
  users.users.git = {
    isSystemUser = true;
    group = "git";
    home = "/var/lib/git-server";
    createHome = true;
    shell = "${pkgs.git}/bin/git-shell";
    openssh.authorizedKeys.keys = [
      # FIXME: Add pubkeys of authorized users
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIF38sHxXn/r7KzWL1BVCqcKqmZA/V76N/y5p52UQghw7 example"
    ];
  };
  users.groups.git = {};
  services.openssh = {
    enable = true;
    extraConfig = ''
      Match user git
        AllowTcpForwarding no
        AllowAgentForwarding no
        PasswordAuthentication no
        PermitTTY no
        X11Forwarding no
    '';
  };
}
</syntaxhighlight>
== Usage ==
1. Run this on the server to create repo <code>myproject</code> accessible by user <code>git</code>
<syntaxhighlight lang="bash">
sudo -u git bash -c "git init --bare ~/myproject.git"
</syntaxhighlight>
(<code>~</code> here is the home of the user <code>git</code>, which is <code>/var/lib/git-server</code>)
2. Push to the server repo from another system
<syntaxhighlight lang="bash">
mkdir myproject
cd myproject
echo hello > a
git init
git add .
git commit -m init
git remote add origin git@myserver:myproject.git
git push origin master
</syntaxhighlight>
3. Clone and edit the server repo from another system
<syntaxhighlight lang="bash">
git clone git@myserver:myproject.git
cd myproject
cat a
echo world >> a
git commit -am hello
git push origin master
</syntaxhighlight>
== Bisecting Nix regressions ==
{{main|bisecting}}
[[Category:Applications]]
[[Category:CLI Applications]]
[[Category:Version control]]
Retrieved from "https://wiki.nixos.org/wiki/Git"