A global .gitignore file allows you to specify patterns for files and directories that should be ignored by Git across all repositories on your system.

A colleague of mine was erroneously placing files in their merge requests that weren’t relevant, and I took the opportunity to educate them as well as share the knowledge more broadly, even if some consider it very basic information.

macOS and .DS_Store

macOS creates a .DS_Store file inside any directory you view with Finder. This has always annoyed me about using a Mac for casual editing. If you consult man git-config, you will come across a method to ignore this across all repositories instead of modifying each one with a .gitignore.

core.excludesFile -
Specifies the pathname to the file that contains patterns to describe paths that are not meant to be tracked, in addition to .gitignore (per-directory) and .git/info/exclude. Defaults to $XDG_CONFIG_HOME/git/ignore. If $XDG_CONFIG_HOME is either not set or empty, $HOME/.config/git/ignore is used instead. See gitignore(5).

Success! This is exactly what we need.

Here is a step-by-step guide to create a global .gitignore file

  1. Create the .config directory and the accompanying ignore file. Since this is macOS, you will not have any of the XDG variables, so we use the fallback paths instead.

     mkdir -p ~/.config/git/
 touch ~/.config/git/ignore

  2. Add the patterns for the files you want to ignore, in this case the dreaded .DS_Store files. You can also take this opportunity to include other things you wish to ignore globally. For example, .swp files come to mind if you are a heavy Vim user.

    Contents of ~/.config/git/ignore:

     # Ignore macOS system files
 .DS_Store

  3. Verify things are working by checking for the presence of a .DS_Store in a git directory.

     % ls -1A
 .DS_Store
 .git
 .github
 .gitmodules
 .submodules
 .vscode
 COPYING
 Containerfile.ArchLinux
 Containerfile.Fedora
 Containerfile.UbuntuLTS
 Containerfile.template
 README.md
 devcontainer.json.template

 % git status
 On branch main
 Your branch is up to date with 'origin/main'.

 nothing to commit, working tree clean

    No .gitignore for this repository and no pending changes!

Wrapping Up

This wasn’t a particularly exciting post, but it was something that had cropped up working with a junior engineer. Sometimes it is easy to forget that I was once green too. Educating others instead of judging is the better path forward. Something about rising tides and boats comes to mind.