RJGit

require "rjgit"
include RJGit

repo = Repo.new("repo.git")

repo = Repo.new("repo.git", :create => true)
repo = Repo.new("repo.git", :create => true, :is_bare => true) # Create a 'bare' git repo.
repo.bare? # Is this a bare repository?

repo.commits('master')
repo.commits('959329025f67539fb82e76b02782322fad032821')
repo.head
commit = repo.commits('master').first # a Commit object; try commit.actor, commit.id, etc.

repo.branches

repo.find('959329025f67539fb82e76b02782322fad032821')
repo.find('959329025f67539fb82e76b02782322fad032821', :commit) # Find a specific :commit, :blob, :tree, or :tag

blob = repo.blob("example/file.txt") # Retrieve a file by filepath, from the HEAD commit...
blob = repo.blob("example/file.txt", "refs/heads/mybranch') # Retrieve the same file from a different branch
blob = repo.find("959329025f67539fb82e76b02782322fad032822", :blob) # ...or by SHA
blob.data # Cat the file; also blob.id, blob.mode, etc.
tree = repo.tree("example") # Retrieve a tree by filepath...
tree = repo.find("959329025f67539fb82e76b02782322fad032000", :tree) #...or by SHA
tree.data # List the tree's contents (blobs and trees). Also tree.id, tree.mode, etc.
tree.each {|entry| puts entry.inspect} # Loop over the Tree's children (Blobs and Trees)
tree.find_blob {|entry| entry[:name] == 'foo.txt'} # Find a single blob that matches the block
tree.find_tree {|entry| entry[:name] == 'mytree' } # Find a single tree that matches the block
tree.find {|entry| ...} # Find a single entry that matches the block
tree.find_all {|entry entry[:name].include?('.') } # Find all entries matching the block
tree.trees # An array of the Tree's child Trees
tree.blobs # An array of the Tree's child Blobs
Porcelain::ls_tree(repo, repo.tree("example"), :print => true, :recursive => true, :ref => 'mybranch') # Outputs the Tree's contents to $stdout. Faster for recursive listing than Tree#each. Passing nil as the second argument lists the entire repository. ref defaults to HEAD.

tag = repo.tags['example_tag']
tag.id # tag's object id
tag.author.name # Etcetera
some_object = Porcelain.object_for_tag(repo, tag) # Returns the tagged object; e.g. a Commit

repo.notes
note = repo.head.note
note.message # the String message of the note
note.annotates # the SHA ID of the object this note is attached to
repo.head.note = "Happy note writing"
repo.head.note_remove

sha1 = repo.head.id
sha2 = repo.commits.last.id
options = {:old_rev => sha2, :new_rev => sha1, :file_path => "some/path.txt", :patch => true}
Porcelain.diff(repo, options)

repo.git.log # Returns an Array of Commits constituting the log for the default branch
repo.git.log("follow-rename.txt", "HEAD", follow: true, list_renames: true) # Log for a specific path, tracking the pathname over renames. Returns an Array of TrackingCommits, which store the tracked filename: [#<RJGit::TrackingCommit:0x773014d3 @tracked_pathname="follow-rename.txt" ...>]

blob = Blob.new_from_string(repo, "Contents of the new blob.") # Inserts the blob into the repository, returns an RJGit::Blob
tree = Tree.new_from_hashmap(repo, {"newblob" => "contents", "newtree" => { "otherblob" => "this blob is contained in the tree 'newtree'" } } ) # Constructs the tree and its children based on the hashmap and inserts it into the repository, returning an RJGit::Tree. Tree.new_from_hashmap takes an RJGit::Tree as an optional third argument, in which case the new tree will consist of the children of that Tree *plus* the contents of the hashmap.

repo.create_branch('new_branch') # Similarly for deleting, renaming
repo.checkout('new_branch')
repo.add('new_file.txt') # Similarly for removing
repo.commit('My message')
repo.update_ref(commit) # Fast forward HEAD (or another ref) to the commit just created

repo = repo.new("repo.git")
tree = Tree.new_from_hashmap(repo, {"newblob" => "contents"}, repo.head.tree ) # As above, use the current head commit's tree as a starting point and add "newblob"
actor = RJGit::Actor.new("test", "test@repotag.org")
commit = Commit.new_with_tree(repo, tree, "My commit message", actor) # Create a new commit with tree as base tree

pack = RJGitReceivePack.new(repo) # Implement the smart-http protocol with RJGitReceivePack and RJGitUploadPack
pack.receive(client_msg) # Respond to a client's GET request
repo.config['remote origin']['url'] # Retrieve config values
Porcelain::diff(repo, options)
Porcelain::blame(repo, options)