Hacky Lua script to confirm any pushes to your main (or protected) git branch

pre-push.lua

#!/usr/bin/lua

--[[
  +-------------------+
  + Lua pre-push hook +
  +-------------------+

  - Prompts user to confirm remote pushes when working on a
    protected branch and pushing to a _protected_ branch.
  - Can be installed locally or globally. I usually
    keep my config files in a dedicated directory and
    create symlinks.
    - Locally: you can place the file in your .git/hooks/pre-push
    - Globally: create a directory for your hooks, e.g
      ~/.git/hooks and add it to your global .gitconfig
      under [core]. 
      e.g vim ~/.gitconfig
      + [core]
      +   hooksPath = /home/matei/.git/hooks
    - chmod +x pre-push
   - You can add your own protected branches (or repositories) to the
     respective maps. If you want it enabled by default, delete the
     repository logic.
   - I left all my comments in, on the off chance that they're helpful.
   
   NOTE: you need to have a lua interpreter installed to execute this!
   https://www.lua.org/pil/1.4.html
   
   Last but not least, I'm still learning Lua, this is just a hacky script! :)
  
--]]

-- I think technically this will only work if we're on that branch?
-- gotta RTFM.
local CMD_GIT_BRANCH = 'git rev-parse --abbrev-ref HEAD'

local CMD_GIT_REPO = 'git rev-parse --show-toplevel'

local PROTECTED_BRANCHES = {['main'] = true, ['master'] = true, ['add-git-hook'] = true}

local PROTECTED_REPOS = {['linkerd2'] = true, ['linkerd2-proxy'] = true, ['dotfiles'] = true}

local ANSI_RED = "\27[31m"
local ANSI_RESET = "\27[0m"
local ANSI_WHITE_BOLD = "\27[37;1;4m" -- 4 is for underline
local ANSI_BOLD = "\27[1m"
local ANSI_GREEN = "\27[32m"
local HOOK_NAME = "\27[96;4m[git-push-hook-check]\27[0m "

-- Execute takes in a command as a string and calls out into the shell to
-- execute it. We start a sub process using `io.popen` and then use the handle
-- to read the output from the command.
local function execute(command)
  local handle = assert(io.popen(command))
  -- `*a` reads it all
  -- https://www.lua.org/manual/5.1/manual.html#pdf-file:read
  local output = handle:read("*a")
  handle:close()
  return output
end

-- Try execute will execute a command via a protected call (pcall). Pcall
-- will return a success boolean and an error message if the inner call
-- fails. We use it to bubble up errors, e.g socket errors from subprocs.
-- If the call fails, we exit with an error, otherwise, we return the output
-- from 'execute'.
local function try_execute(command)
  local success, data = pcall(execute, command)
  if not success then
    os.exit(2)
  end
  return data
end

local repo_path = try_execute(CMD_GIT_REPO)
-- Will capture string after last '/' to get the name of the repository.
local repo_name = string.match(repo_path, "/%a+/.+/(%a+)")
if not PROTECTED_REPOS[repo_name] then
  os.exit()
end

local branch_name = try_execute(CMD_GIT_BRANCH)
branch_name = string.gsub(branch_name, '\n', '')
if PROTECTED_BRANCHES[branch_name] then
  -- colors!
  local push_msg = HOOK_NAME..ANSI_GREEN.."\27[4;1mSure\27[0;32m you want to push to ["..ANSI_WHITE_BOLD..branch_name..ANSI_RESET..ANSI_GREEN.."]?"..ANSI_RESET..ANSI_BOLD.." (Y/n)"..ANSI_RESET
  local confirm
  repeat
    print(push_msg)
    -- Take input from controlling terminal
    local tty_handle = io.open("/dev/tty")
    confirm = tty_handle:read(1)
    if not confirm then return end   -- no input
    confirm = confirm:lower()
  until confirm == "y" or confirm == "n"
  if confirm ~= "y" then
    print(HOOK_NAME..ANSI_RED.."Push to ["..ANSI_WHITE_BOLD..branch_name..ANSI_RESET..ANSI_RED.."] aborted"..ANSI_RESET)
    os.exit(1)
  end
  return
end
os.exit()