Git prepare-commit-msg hook

README.md

Summary

This hook automatically inserts an appropriate filename description in the suggested commit message for each commit you make which touches a single file.

Examples

These are inserted as the first line of the message opened in your editor when running git commit. Messages entered with -m will not be affected:

If you've only touched a single static method

User::create: 

If you've only touched a single instance method

User->getName:

If you've only touched a single file, and none of the above apply

User: 

Limitations

This is currently only made to work with PHP files: if only one method is touched, it will insert the method name as part of the description.

prepare-commit-msg

#!/usr/bin/env ruby
# MIT License

# Copyright (c) 2020 iFixit

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

message_file = ARGV[0]
type = ARGV[1]
case type
when 'message', 'merge', 'squash'
   # When the user passes `-m` on the CLI, don't touch it
   return
end

def matches_once(lines, regex)
  matches = lines.select { |i| regex =~ i }
  matches.length == 1
end

def for_single_match(lines, regexes)
  one_time = regexes.select { |re| matches_once(lines, re) }
  pp one_time
  return if one_time.empty?

  matching = one_time[0]

  matches = lines.select { |i| matching =~ i }
  yield matches[0] if matches.length == 1
end

def get_method_name(filename, function)
  match = /function\s+(\w+)\s*\(/.match(function)
  return filename unless match

  function_name = match[1]
  if /static/ =~ function
    "#{filename}::#{function_name}"
  else
    "#{filename}->#{function_name}"
  end
end

def get_suggestion(filename)
  for_single_match(
    `git diff --cached`.each_line,
    [/^\+.*function\s+\w/, /^\-.*function\s+\w/, /function\s+\w/]
  ) do |function|
    return get_method_name(filename, function)
  end
  for_single_match(
    `git diff --cached`.each_line,
    [/class\s+\w/]
  ) do |classname|
     match = /class\s+(\w+)/.match(classname)
     return match[1]
  end
  filename
end

status = `git status  --porcelain`
for_single_match status.each_line, [/^M/] do |changed_file|
  match = /^M..(.*)\.\w+$/.match(changed_file)
  description = get_suggestion(File.basename(match[1]))
  suggested = "#{description}: \n"
  message = IO.read(message_file)
  IO.write(message_file, suggested + message)
end