a better git grep

gg.rb

#! /usr/bin/env ruby

USAGE = "gg <git-repos> pattern [-r]

Git grep for pattern using:
 - <git-repos> are passed in, or
 - the current dir is in a git repo, or,
 - git repos that are subdirs ofthe current dir

If `-r' is specified, git grep from the repo's
root directory. Only works if the current dir
is a git repo."

class GitGrep
  CMD = "git grep --break -n %s"

  def initialize(pattern, repos, options = {})
    @pattern = pattern
    @repos = repos
    @options = options
  end

  def grep
    @repos.each do |repo|
      if @options[:grep_from_root]
        Dir.chdir(repo) { grep_repo repo }
      else
        grep_repo repo
      end
    end
  end

  private
    def grep_repo(repo)
      IO.popen(CMD % @pattern).each do |line|
        puts line
      end
    end
end

def main
  pattern = nil
  grep_from_root = nil
  repos = []

  argv = ARGV.dup
  if argv.member?("-r")
    argv.delete "-r"
    grep_from_root = true
  end

  if argv.size == 0
    puts USAGE
    exit 1
  elsif argv.size == 1
    pattern = argv.first
  else
    *repos, pattern = argv
  end

  if repos.empty?
    # No repos passed in
    in_git_repo = begin
                    `git rev-parse 2>/dev/null`
                    $?.exitstatus.zero?
                  end
    if in_git_repo
      repos << `git rev-parse --show-toplevel`.chomp
    else
      Dir['*'].each do |x|
        next unless File.directory? File.join(x, ".git")
        repos << x
      end
    end

  end

  GitGrep.new(pattern, repos,
              grep_from_root: grep_from_root).grep
end

if $0 == __FILE__
  main
end