Grack - Ruby/Rack Git Smart HTTP Server Handler

This project aims to replace the builtin git-http-backend CGI handler distributed with C Git with a Rack application.

• Homepage :: https://github.com/grackorg/grack
• Source :: https://github.com/grackorg/grack.git

This project aims to replace the builtin git-http-backend CGI handler distributed with C Git with a Rack application. By default, Grack uses calls to git on the system to implement Smart HTTP. Since the git-http-backend is really just a simple wrapper for the upload-pack and receive-pack processes with the '--stateless-rpc' option, this does not actually re-implement very much. However, it is possible to use a different backend by specifying a different Adapter.

The default git-http-backend only runs as a CGI script, and specifically is only targeted for Apache 2.x usage (it requires PATH_INFO to be set and specifically formatted). So, instead of trying to get it to work with other CGI capable webservers (Lighttpd, etc), we can get it running on nearly every major and minor webserver out there by making it Rack capable. Rack applications can run with the following handlers:

• CGI
• FCGI
• Mongrel (and EventedMongrel and SwiftipliedMongrel)
• WEBrick
• SCGI
• LiteSpeed
• Thin

These web servers include Rack handlers in their distributions:

• Ebb
• Fuzed
• Phusion Passenger (which is mod_rack for Apache and for nginx)
• Unicorn

With Warbler, and JRuby, we can also generate a WAR file that can be deployed in any Java web application server (Tomcat, Glassfish, Websphere, JBoss, etc).

By default, Grack uses calls to git on the system to implement Smart HTTP. Since the git-http-backend is really just a simple wrapper for the upload-pack and receive-pack processes with the '--stateless-rpc' option, this does not actually re-implement very much. However, it is possible to use a different backend by specifying a different Adapter. See below for a list.

Note that while it is technically possible to host non-bare repositories with this gem, it is discouraged. The only somewhat safe option is to serve such a repository as read-only since there is a greater risk of arbitrary filesystem traversal when a checkout tree must be traversed to reach the repository administrative area (.git directory). Additionally, any recent version of Git prevents pushes into non-bare repositories by default since pushing into the currently checked out branch can effectively "break" the checkout tree.

In config.ru:

require 'grack/app'
require 'grack/git_adapter'

config = {
  :root => '/path/to/bare/repositories',
  :allow_push => true,
  :allow_pull => true,
  :git_adapter_factory => ->{ Grack::GitAdapter.new }
}

run Grack::App.new(config)

Then run:

$ bundle exec rackup --host 127.0.0.1 --port 8080 config.ru
$ git clone http://localhost:8080/your-repository.git

Grack makes calls to the git binary through the GitAdapter abstraction class. Grack can be made to use a different backend by specifying a call-able object, such as a lambda, in Grack's configuration that provides new adapter instances per request. For example:

Grack::App.new(:git_adapter_factory => ->{ MyAdapter.new })

Alternative adapters available:

• rjgit_grack lets Grack use the RJGit gem to implement Smart HTTP in pure JRuby.

Adapters are abstraction classes that handle the actual implementation of the Smart HTTP protocol (advertising refs, uploading and receiving packfiles). Such abstraction classes must have the following methods:

MyAdapter.repository_path=(repository_path)
MyAdapter.exist?
MyAdapter.handle_pack(kind, io_in, io_out, opts = {})
MyAdapter.file(path)
MyAdapter.update_server_info
MyAdapter.allow_push?
MyAdapter.allow_pull?

See Grack::GitAdapter for more detailed documentation and an example implementation.

• Supports Git Smart HTTP protocol.
• Supports Git Basic HTTP protocol.
• Limits push/pull access globally and per-repository.
• Thread safe operation.

By default, grack doesn't support git hooks. This is because the default GitAdapter directly streams the requests to the git-receive-pack and git-upload-pack processes. However, alternative adapters may implement hooks.

Adapters that support hooks:

• rjgit_grack

• Will likely block fully evented web servers when using the stock Git adapter.

• Ruby >=1.9.3
• Git >=1.7 (if using the included Git adapter)
• rack (>= 0)

• All runtime requirements
• rake (>= 12.3.3, ~> 12.3.3)
• rack-test (~> 0.6, >= 0.6.3)
• minitest (>= 5.8.0, ~> 5.8)
• mocha (>= 1.1.0, ~> 1.1)
• simplecov (>= 0.10.0, ~> 0.10)
• yard (~> 0.9.24)
• redcarpet (>= 3.1.0, ~> 3.1)
• github-markup (~> 1.0, >= 1.0.2)
• pry (~> 0)

Contributions for bug fixes, documentation, extensions, tests, etc. are encouraged.

1. Clone the repository.
2. Fix a bug or add a feature.
3. Add tests for the fix or feature.
4. Make a pull request.

After checking out the source, run:

$ bundle install
$ bundle exec rake test yard

This will install all dependencies, run the tests/specs, and generate the documentation.

Thanks to all contributors. Without your help this project would not exist.

• Scott Chacon :: schacon@gmail.com
• Dawa Ometto :: d.ometto@gmail.com
• Jeremy Bopp :: jeremy@bopp.net

(The MIT License)

Copyright (c) 2015 Scott Chacon <schacon@gmail.com>

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'Software'), to deal in the Software without restriction, including
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