$ pry
[1] pry(main)> require 'rugged'
=> true
[2] pry(main)> repo=Rugged::Repository.new '.'
=> #<Rugged::Repository:0xb70b9b4c>
[3] pry(main)> author={ :email=>'[email protected]', :time=>Time.now, :name=>'Jeff Welling' }
=> {:email=>"[email protected]",
 :time=>Sat Sep 29 11:38:05 -0700 2012,
 :name=>"Jeff Welling"}
[4] pry(main)> parents=[ repo.lookup( repo.head.target ).oid ]=> ["300febdd0d599ae44c529004fb438a25495750b3"]
[5] pry(main)> puts `git status`# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#	new file:   second_fakefile
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	fakedir/
=> nil
[6] pry(main)> tree= repo.lookup( repo.index.write_tree )
=> #<Rugged::Tree:0xb709dd48
 @owner=
  #<Rugged::Repository:0xb70b9b4c
   @index=
    #<Rugged::Index:0xb709dd84 @owner=#<Rugged::Repository:0xb70b9b4c ...>>>>
[7] pry(main)>
[8] pry(main)> puts `git cat-file #{tree.oid}`
usage: git cat-file (-t|-s|-e|-p|<type>|--textconv) <object>
   or: git cat-file (--batch|--batch-check) < <list_of_objects>

<type> can be one of: blob, tree, commit, tag
    -t                    show object type
    -s                    show object size
    -e                    exit with zero when there's no error
    -p                    pretty-print object's content
    --textconv            for blob objects, run textconv on object's content
    --batch               show info and content of objects fed from the standard input
    --batch-check         show info about objects fed from the standard input


=> nil
[9] pry(main)> puts `git cat-file -p #{tree.oid}`
100644 blob e69de29bb2d1d6434b8b29ae775ad8c2e48c5391	fakefile
100644 blob e69de29bb2d1d6434b8b29ae775ad8c2e48c5391	second_fakefile
=> nil
[10] pry(main)> x=Rugged::Commit.create( repo, :author=>author, :message=>"Hello world\n\n", :committer=>author, :parents=>parents, :tree=>tree )
TypeError: wrong argument type nil (expected String)
from (pry):9:in `create'
[11] pry(main)>