Use a less error-prone way of specifying gem files

[mattbrictson]

Before, whenever a new file is added to lib, the contributor or maintainer has to remember to explicitly add it to the gemspec. If this step is forgotten, it results in a broken release, like #657.

This commit makes this process less error prone by using git ls-files to automatically include all appropriate files in the gem. This is in line with what is advocated by Bundler's gem template:

https://github.com/bundler/bundler/blob/2a4d88a7044528209321fd4441e995ec66f604b9/lib/bundler/templates/newgem/newgem.gemspec.tt#L26

To test this PR I ran rake gem and verified that the list of files included in the gem is the same as before:

AUTHORS.rdoc
CHANGELOG.rdoc
README.rdoc
RELEASE.rdoc
TODO.rdoc
annotate.gemspec
bin/annotate
lib/annotate.rb
lib/annotate/active_record_patch.rb
lib/annotate/annotate_models.rb
lib/annotate/annotate_routes.rb
lib/annotate/constants.rb
lib/annotate/parser.rb
lib/annotate/tasks.rb
lib/annotate/version.rb
lib/generators/annotate/USAGE
lib/generators/annotate/install_generator.rb
lib/generators/annotate/templates/auto_annotate_models.rake
lib/tasks/annotate_models.rake
lib/tasks/annotate_models_migrate.rake
lib/tasks/annotate_routes.rake

[drwl]

@mattbrictson oh wow this is neat, thanks for the PR. Having this would have definitely prevented an issue like #657. Two things:

1. looks like it's just missing LICENSE.txt, should be an easy fix.
2. what's the difference between using the -z flag and splitting on \x0 compared to not using -z flag and splitting on \n, for example like how Pry does it?

[mattbrictson]

looks like it's just missing LICENSE.txt, should be an easy fix.

Nice catch, I'll add it.

what's the difference between using the -z flag and splitting on \x0 compared to not using -z flag and splitting on \n, for example like how Pry does it?

I assume that if you run the code on a Windows machine then the line ending will not be \n, so it would break in that environment. The -z is therefore more robust across platforms.

Alternatively you could require "English" and then split on $RS (the platform-specific line separator), but the -z trick is a lot more concise.

[drwl]

Gotcha thanks for the explanation, I learned something 🙂.