Git pre-push hook that runs Rubocop on files that have been added or modified on the current branch

pre-push.sh

#!/usr/bin/env sh

# If you don't already have a pre-push hook in your working copy, simply copy 
# this into .git/hooks/pre-push in your working copy. If you already have a 
# pre-push hook, you'll have to integrate it with your existing hook.

function current_branch {
  git rev-parse --abbrev-ref HEAD
}

# The point at which the current branch diverges from master
function merge_base {
  git merge-base $(current_branch) master
}

function files_added_or_modified_on_current_branch {
  git diff --diff-filter=AM --name-only $(merge_base)
}

# Run rubocop on .rb files that have been added or modified on the current branch
rubocop --force-exclusion $(files_added_or_modified_on_current_branch | grep -E '\.(rb|rake)$|^Gemfile')