Git pre-commit hooks only for a specific subfolder?

Question

I currently have a single repo with two projects, each in their own subfolder: one in C# and one in Javascript. I want to have a pre-commit hook that will run jshint but only if any of the staged files are in the Javascript folder If the staged files are only from the C# folder, then the pre-commit hook won't run.

Is it that possible at all? Or is my only solution to split the two projects into their own repos?

Answer 1

Specify files to include (or exclude to exclude) specific directories, e.g. run hooks only in my_dir:

files: ^my_dir/
repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    hooks:
        ...

or run everywhere but inside my_dir:

exclude: ^my_dir/
repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    hooks:
        ...

If you have a long list of exclusions, use verbose regex:

exclude: >
  (?x)^(
      path/to/file1.py|
      path/to/file2.py|
      path/to/file3.py
  )$

you can also apply these to specific hooks only, just do:

-   id: my-hook
    exclude: ^my_dir/

Answer 2

You can use git log to find out if the latest commit in a subdir matches the latest commit at your repository root:

#!/bin/env bash

function get_commit {
    git log --oneline -- $1 | head -n 1 | cut -d " " -f1
}

ROOT_COMMIT=$(get_commit)
SUBDIR_COMMIT=$(get_commit my/subdir/path)

if [ "$SUBDIR_COMMIT" == "$ROOT_COMMIT" ]; then
    # do pre-commit hook stuff here
fi