Grit

Grit gives you object oriented read/write access to Git repositories via Ruby. The main goals are stability and performance. To this end, some of the interactions with Git repositories are done by shelling out to the system's git command, and other interactions are done with pure Ruby reimplementations of core Git functionality. This choice, however, is transparent to end users, and you need not know which method is being used.

This software was developed to power GitHub, and should be considered production ready. An extensive test suite is provided to verify its correctness.

Grit is maintained by Tom Preston-Werner, Scott Chacon, Chris Wanstrath, and PJ Hyett.

This documentation is accurate as of Grit 2.3.

Requirements

git (http://git-scm.com) tested with 1.7.2.1

Install

Easiest install is via RubyGems:

$ gem install grit

Source

Grit's Git repo is available on GitHub, which can be browsed at:

http://github.com/mojombo/grit

and cloned with:

git clone git://github.com/mojombo/grit.git

Development

You will need these gems to get tests to pass:

mocha

Contributing

If you'd like to hack on Grit, follow these instructions. To get all of the dependencies, install the gem first.

Fork the project to your own account
Clone down your fork
Create a thoughtfully named topic branch to contain your change
Hack away
Add tests and make sure everything still passes by running rake
If you are adding new functionality, document it in README.md
Do not change the version number, I will do that on my end
If necessary, rebase your commits into logical chunks, without errors
Push the branch up to GitHub
Send a pull request for your branch

Usage

Grit gives you object model access to your Git repositories. Once you have created a Repo object, you can traverse it to find parent commits, trees, blobs, etc.

Initialize a Repo object

The first step is to create a Grit::Repo object to represent your repo. In this documentation I include the Grit module to reduce typing.

require 'grit'
repo = Grit::Repo.new("/Users/tom/dev/grit")

In the above example, the directory /Users/tom/dev/grit is my working directory and contains the .git directory. You can also initialize Grit with a bare repo.

repo = Repo.new("/var/git/grit.git")

Getting a list of commits

From the Repo object, you can get a list of commits as an array of Commit objects.

repo.commits
# => [#<Grit::Commit "e80bbd2ce67651aa18e57fb0b43618ad4baf7750">,
      #<Grit::Commit "91169e1f5fa4de2eaea3f176461f5dc784796769">,
      #<Grit::Commit "038af8c329ef7c1bae4568b98bd5c58510465493">,
      #<Grit::Commit "40d3057d09a7a4d61059bca9dca5ae698de58cbe">,
      #<Grit::Commit "4ea50f4754937bf19461af58ce3b3d24c77311d9">]

Called without arguments, Repo#commits returns a list of up to ten commits reachable by the master branch (starting at the latest commit). You can ask for commits beginning at a different branch, commit, tag, etc.

repo.commits('mybranch')
repo.commits('40d3057d09a7a4d61059bca9dca5ae698de58cbe')
repo.commits('v0.1')

You can specify the maximum number of commits to return.

repo.commits('master', 100)

If you need paging, you can specify a number of commits to skip.

repo.commits('master', 10, 20)

The above will return commits 21-30 from the commit list.

The Commit object

Commit objects contain information about that commit.

head = repo.commits.first

head.id
# => "e80bbd2ce67651aa18e57fb0b43618ad4baf7750"

head.parents
# => [#<Grit::Commit "91169e1f5fa4de2eaea3f176461f5dc784796769">]

head.tree
# => #<Grit::Tree "3536eb9abac69c3e4db583ad38f3d30f8db4771f">

head.author
# => #<Grit::Actor "Tom Preston-Werner <tom@mojombo.com>">

head.authored_date
# => Wed Oct 24 22:02:31 -0700 2007

head.committer
# => #<Grit::Actor "Tom Preston-Werner <tom@mojombo.com>">

head.committed_date
# => Wed Oct 24 22:02:31 -0700 2007

head.message
# => "add Actor inspect"

You can traverse a commit's ancestry by chaining calls to #parents.

repo.commits.first.parents[0].parents[0].parents[0]

The above corresponds to master^^^ or master~3 in Git parlance.

The Tree object

A tree records pointers to the contents of a directory. Let's say you want the root tree of the latest commit on the master branch.

tree = repo.commits.first.tree
# => #<Grit::Tree "3536eb9abac69c3e4db583ad38f3d30f8db4771f">

tree.id
# => "3536eb9abac69c3e4db583ad38f3d30f8db4771f"

Once you have a tree, you can get the contents.

contents = tree.contents
# => [#<Grit::Blob "4ebc8aea50e0a67e000ba29a30809d0a7b9b2666">,
      #<Grit::Blob "81d2c27608b352814cbe979a6acd678d30219678">,
      #<Grit::Tree "c3d07b0083f01a6e1ac969a0f32b8d06f20c62e5">,
      #<Grit::Tree "4d00fe177a8407dbbc64a24dbfc564762c0922d8">]

This tree contains two Blob objects and two Tree objects. The trees are subdirectories and the blobs are files. Trees below the root have additional attributes.

contents.last.name
# => "lib"

contents.last.mode
# => "040000"

There is a convenience method that allows you to get a named sub-object from a tree.

tree / "lib"
# => #<Grit::Tree "e74893a3d8a25cbb1367cf241cc741bfd503c4b2">

You can also get a tree directly from the repo if you know its name.

repo.tree
# => #<Grit::Tree "master">

repo.tree("91169e1f5fa4de2eaea3f176461f5dc784796769")
# => #<Grit::Tree "91169e1f5fa4de2eaea3f176461f5dc784796769">

The Blob object

A blob represents a file. Trees often contain blobs.

blob = tree.contents.first
# => #<Grit::Blob "4ebc8aea50e0a67e000ba29a30809d0a7b9b2666">

A blob has certain attributes.

blob.id
# => "4ebc8aea50e0a67e000ba29a30809d0a7b9b2666"

blob.name
# => "README.txt"

blob.mode
# => "100644"

blob.size
# => 7726

You can get the data of a blob as a string.

blob.data
# => "Grit is a library to ..."

You can also get a blob directly from the repo if you know its name.

repo.blob("4ebc8aea50e0a67e000ba29a30809d0a7b9b2666")
# => #<Grit::Blob "4ebc8aea50e0a67e000ba29a30809d0a7b9b2666">

Other

There are many more API methods available that are not documented here. Please reference the code for more functionality.

chipiga/grit