Git Exclude Folder: Explained

1st January 2024 - Monday

A cartoon image depicting a bipedal octo-cat with pink skin, green eyes, and blue suckers on his tentacles. The octo-cat has white whiskers and bushy white mustache and eyebrows. He is wearing a suit vest with dress shirt, pants, and a tie teaching a complex topic using many charts, graphs and diagrams written on a chalkboard. There is a single student wearing a suit that is probably a school uniform.

To exclude a directory from git diff, use the following command:

git diff -- . ':!directory_name'

You can find this exceptionally terse answer at at least a dozen search results, but not a single one offers an explanation. Well, that's not enough info for me...

The "pathspec" is documented under git help gitglossary and is used for many git commands even if their syntax statement shows <path> instead of <pathspec> :

https://git-scm.com/docs/gitglossary#def_pathspec

Here are the important points:

The double dashes (--) followed by a space means end of command line flags. Without this, git may try to interpret your pathspec as a command line flag.
The dot (.) means the current directory. I don't think this is really necessary.
The colon (:) indicates that the characters which follow it are a "magic signature".
The exclamation mark means "exclude".
The "magic signature" should be terminated by another colon, but that's optional if the pattern begins with a less magical symbol.

I wanted to see what had changed in an Eleventy site, excluding the generated output files. So, here's the command I used:

git status -- ':!:_output'

Note that I needed to terminate the magic signature with another colon because the path I wanted to exclude started with an underscore (_). Without that second colon, I got an error message:

fatal: Unimplemented pathspec magic '_' in ':!_output'`