git hook to run a command after `git pull` if a specified file was changed. In this example it's used to update your python virtual environment if the requirements file has changed. Run `chmod +x post-merge` to make it executable then put it into git hooks folder (`.git/hooks/` by default)

post-merge

#!/usr/bin/env bash
# MIT © Sindre Sorhus - sindresorhus.com
# Krishna Vadakattu - vadakattu.com

# git hook to run a command after `git pull` if a specified file was changed.
# Run `chmod +x post-merge` to make it executable then put it into git hooks folder (`.git/hooks/` by default)

changed_files="$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)"

check_run() {
	echo "$changed_files" | grep --quiet "$1" && eval "$2"
}

# Example usage
# In this example it's used to update your python virtual environment if the requirements file has changed.
check_run requirements.txt "pip install -r requirements.txt"