git hook to run a command after `git pull` if a specified file was changed.In this example it's used to run `npm install` if package.json changed and `bower install` if `bower.json` changed.Run `chmod +x post-merge` to make it executable then put it into `.git/hooks/`.

post-merge

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

# git hook to run a command after `git pull` or `git checkout` if a specified file was changed
# Run `chmod +x post-checkout` to make it executable then put it into `.git/hooks/`.

changed_files="$(git diff-tree -r --name-only --no-commit-id HEAD@{1} HEAD)"

check_run() {
	echo "$changed_files" | grep --quiet "$1" && echo " * changes detected in $1" && echo " * running $2" && eval "$2"
}
 
# Example usage
# In this example it's used to run `npm install` if package.json changed and `bower install` if `bower.json` changed.
check_run package.json "npm install && npm prune"
check_run bower.json "bower install && bower prune"

https://stackoverflow.com/questions/3462955/putting-git-hooks-into-repository/3464399#3464399