Pre-push

Available in Git 1.8.2 and above.

Pre-push hooks can be used to prevent a push from going though. Reasons this is helpful include: blocking accidental manual pushes to specific branches, or blocking pushes if an established check fails (unit tests, syntax).

A pre-push hook is created by simply creating a file named pre-push under .git/hooks/, and (gotcha alert), making sure the file is executable: chmod +x ./git/hooks/pre-push.

Here’s an example from Hannah Wolfe that blocks a push to master:

#!/bin/bash

protected_branch='master'  
current_branch=$(git symbolic-ref HEAD | sed -e 's,.*/\(.*\),\1,')

if [ $protected_branch = $current_branch ]  
then  
    read -p "You're about to push master, is that what you intended? [y|n] " -n 1 -r < /dev/tty
    echo
    if echo $REPLY | grep -E '^[Yy]$' > /dev/null
    then
        exit 0 # push will execute
    fi
    exit 1 # push will not execute
else  
    exit 0 # push will execute
fi

Here’s an example from Volkan Unsal which makes sure RSpec tests pass before allowing the push:

#!/usr/bin/env ruby
require 'pty'
html_path = "rspec_results.html"
begin
  PTY.spawn( "rspec spec --format h > rspec_results.html" ) do |stdin, stdout, pid|
  begin
    stdin.each { |line| print line }
  rescue Errno::EIO
  end
end
rescue PTY::ChildExited
  puts "Child process exit!"
end

# find out if there were any errors  
html = open(html_path).read
examples = html.match(/(\d+) examples/)[0].to_i rescue 0
errors = html.match(/(\d+) errors/)[0].to_i rescue 0
if errors == 0 then
  errors = html.match(/(\d+) failure/)[0].to_i rescue 0
end
pending = html.match(/(\d+) pending/)[0].to_i rescue 0

if errors.zero?
  puts "0 failed! #{examples} run, #{pending} pending"
  # HTML Output when tests ran successfully:
  # puts "View spec results at #{File.expand_path(html_path)}"
  sleep 1
  exit 0
else
  puts "\aCOMMIT FAILED!!"
  puts "View your rspec results at #{File.expand_path(html_path)}"
  puts
  puts "#{errors} failed! #{examples} run, #{pending} pending"
  # Open HTML Ooutput when tests failed
  # `open #{html_path}`
  exit 1
end

As you can see, there are lots of possibilities, but the core piece is to exit 0 if good things happened, and exit 1 if bad things happened. Anytime you exit 1 the push will be prevented and your code will be in the state it was before running git push....

When using client side hooks, keep in mind that users can skip all client side hooks by using the option “–no-verify” on a push. If you’re relying on the hook to enforce process, you can get burned.

Documentation: https://git-scm.com/docs/githooks#_pre_push

Official Sample: https://github.com/git/git/blob/87c86dd14abe8db7d00b0df5661ef8cf147a72a3/templates/hooks–pre-push.sample

Found a mistake? Have a question or improvement idea? Let me know.

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