added a pure-ruby git library and converted the cat_file commands to use it

PURE_TODO

@@ -0,0 +1,32 @@
+This is a listing of all the places I can find that Grit actually does a
+'git' system call.  My goal is to add native Ruby versions of all of them.
+
+Completed
+===========================
+** lib/grit/blob.rb:36:      @size ||= @repo.git.cat_file({:s => true}, id).chomp.to_i
+** lib/grit/blob.rb:43:      @data ||= @repo.git.cat_file({:p => true}, id)
+
+
+Next to do
+===========================
+lib/grit/tree.rb:16:      output = repo.git.ls_tree({}, treeish, *paths)
+lib/grit/config.rb:9:      @repo.git.config({}, key, value)
+lib/grit/config.rb:40:        @repo.git.config(:list => true).split(/\n/)
+lib/grit/tag.rb:28:      output = repo.git.for_each_ref(actual_options, "refs/tags")
+lib/grit/head.rb:37:      output = repo.git.for_each_ref(actual_options, HEAD_PREFIX)
+lib/grit/head.rb:50:        self.new($1, repo.git.rev_parse(options, 'HEAD'))
+
+
+May not be fast enough
+=============================
+lib/grit/commit.rb:74:      repo.git.rev_list({}, ref).strip.split("\n").size
+lib/grit/commit.rb:92:      output = repo.git.rev_list(actual_options, ref)
+lib/grit/commit.rb:94:      output = repo.git.rev_list(actual_options.merge(:all => true))
+lib/grit/blob.rb:58:      data = repo.git.blame({:p => true}, commit, '--', file)
+
+
+More Difficult
+===========================
+lib/grit/commit.rb:39:      @id_abbrev ||= @repo.git.rev_parse({:short => true}, self.id).chomp
+lib/grit/commit.rb:150:      text = repo.git.diff({:full_index => true}, *paths)
+lib/grit/commit.rb:156:        diff = @repo.git.show({:full_index => true, :pretty => 'raw'}, @id)

lib/grit.rb

@@ -11,10 +11,12 @@ require 'timeout'
 require 'rubygems'
 require 'mime/types'
 require 'open4'
+require 'digest/sha1'
 
 # internal requires
 require 'grit/lazy'
 require 'grit/errors'
+require 'grit/git-ruby'
 require 'grit/git'
 require 'grit/ref'
 require 'grit/commit'
@@ -26,6 +28,7 @@ require 'grit/config'
 require 'grit/repo'
 require 'grit/index'
 
+
 module Grit
   class << self
     attr_accessor :debug

lib/grit/git-ruby.rb

@@ -0,0 +1,35 @@
+require 'grit/git-ruby/repository'
+
+module Grit
+  
+  module GitRuby
+    
+    attr_accessor :ruby_gitdir
+    
+    # (raw) allowed_options = [:max_count, :skip, :since, :all]
+    def cat_file(options, ref)
+      if options[:t]
+        file_type(ref)
+        return 
+      elsif options[:s]
+        file_size(ref)
+      elsif options[:p]
+        ruby_git_dir.cat_file(ref)
+      end
+    end
+    
+    def file_size(ref)
+      ruby_git_dir.cat_file_size(ref).to_s
+    end
+    
+    def file_type(ref)
+      ruby_git_dir.cat_file_type(ref)
+    end
+    
+    def ruby_git_dir
+      @ruby_gitdir ||= Repository.new(@git_dir)
+    end
+    
+  end
+  
+end

lib/grit/git-ruby/internal/loose.rb

@@ -0,0 +1,137 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#    Scott Chacon <schacon@gmail.com>
+#
+# provides native ruby access to git objects and pack files
+#
+
+require 'zlib'
+require 'digest/sha1'
+
+require 'grit/git-ruby/internal/raw_object'
+
+module Grit
+  module GitRuby 
+    module Internal
+      class LooseObjectError < StandardError
+      end
+
+      class LooseStorage
+        def initialize(directory)
+          @directory = directory
+        end
+
+        def [](sha1)
+          sha1 = sha1.unpack("H*")[0]
+          begin
+            path = @directory+'/'+sha1[0...2]+'/'+sha1[2..39]
+            get_raw_object(File.read(path))
+          rescue Errno::ENOENT
+            nil
+          end
+        end
+
+        def get_raw_object(buf)
+          if buf.length < 2
+            raise LooseObjectError, "object file too small"
+          end
+
+          if legacy_loose_object?(buf)
+            content = Zlib::Inflate.inflate(buf)
+            header, content = content.split(/\0/, 2)
+            if !header || !content
+              raise LooseObjectError, "invalid object header"
+            end
+            type, size = header.split(/ /, 2)
+            if !%w(blob tree commit tag).include?(type) || size !~ /^\d+$/
+              raise LooseObjectError, "invalid object header"
+            end
+            type = type.to_sym
+            size = size.to_i
+          else
+            type, size, used = unpack_object_header_gently(buf)
+            content = Zlib::Inflate.inflate(buf[used..-1])
+          end
+          raise LooseObjectError, "size mismatch" if content.length != size
+          return RawObject.new(type, content)
+        end
+
+        # currently, I'm using the legacy format because it's easier to do
+        # this function takes content and a type and writes out the loose object and returns a sha
+        def put_raw_object(content, type)
+          size = content.length.to_s
+          LooseStorage.verify_header(type, size)
+          
+          header = "#{type} #{size}\0"
+          store = header + content
+                    
+          sha1 = Digest::SHA1.hexdigest(store)
+          path = @directory+'/'+sha1[0...2]+'/'+sha1[2..40]
+          
+          if !File.exists?(path)
+            content = Zlib::Deflate.deflate(store)
+          
+            FileUtils.mkdir_p(@directory+'/'+sha1[0...2])
+            File.open(path, 'w') do |f|
+              f.write content
+            end
+          end
+          return sha1
+        end
+        
+        # simply figure out the sha
+        def self.calculate_sha(content, type)
+          size = content.length.to_s
+          verify_header(type, size)
+          header = "#{type} #{size}\0"
+          store = header + content
+                    
+          Digest::SHA1.hexdigest(store)
+        end
+        
+        def self.verify_header(type, size)
+          if !%w(blob tree commit tag).include?(type) || size !~ /^\d+$/
+            raise LooseObjectError, "invalid object header"
+          end
+        end
+
+        # private
+        def unpack_object_header_gently(buf)
+          used = 0
+          c = buf[used]
+          used += 1
+
+          type = (c >> 4) & 7;
+          size = c & 15;
+          shift = 4;
+          while c & 0x80 != 0
+            if buf.length <= used
+              raise LooseObjectError, "object file too short"
+            end
+            c = buf[used]
+            used += 1
+
+            size += (c & 0x7f) << shift
+            shift += 7
+          end
+          type = OBJ_TYPES[type]
+          if ![:blob, :tree, :commit, :tag].include?(type)
+            raise LooseObjectError, "invalid loose object type"
+          end
+          return [type, size, used]
+        end
+        private :unpack_object_header_gently
+
+        def legacy_loose_object?(buf)
+          word = (buf[0] << 8) + buf[1]
+          buf[0] == 0x78 && word % 31 == 0
+        end
+        private :legacy_loose_object?
+      end
+    end 
+  end
+end

lib/grit/git-ruby/internal/mmap.rb

@@ -0,0 +1,59 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#    Scott Chacon <schacon@gmail.com>
+#
+# provides native ruby access to git objects and pack files
+#
+
+begin
+  require 'mmap'
+rescue LoadError
+
+module Grit 
+  module GitRuby 
+    module Internal
+      class Mmap
+        def initialize(file)
+          @file = file
+          @offset = nil
+        end
+
+        def unmap
+          @file = nil
+        end
+
+        def [](*idx)
+          idx = idx[0] if idx.length == 1
+          case idx
+          when Range
+            offset = idx.first
+            len = idx.last - idx.first + idx.exclude_end? ? 0 : 1
+          when Fixnum
+            offset = idx
+            len = nil
+          when Array
+            offset, len = idx
+          else
+            raise RuntimeError, "invalid index param: #{idx.class}"
+          end
+          if @offset != offset
+            @file.seek(offset)
+          end
+          @offset = offset + len ? len : 1
+          if not len
+            @file.read(1)[0]
+          else
+            @file.read(len)
+          end
+        end
+      end
+    end
+  end 
+end
+
+end     # rescue LoadError
+

lib/grit/git-ruby/internal/pack.rb

@@ -0,0 +1,275 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#    Scott Chacon <schacon@gmail.com>
+#
+# provides native ruby access to git objects and pack files
+#
+
+require 'zlib'
+require 'grit/git-ruby/internal/raw_object'
+require 'grit/git-ruby/internal/mmap'
+
+module Grit 
+  module GitRuby 
+    module Internal
+      class PackFormatError < StandardError
+      end
+
+      class PackStorage
+        OBJ_OFS_DELTA = 6
+        OBJ_REF_DELTA = 7
+
+        FanOutCount = 256
+        SHA1Size = 20
+        IdxOffsetSize = 4
+        OffsetSize = 4
+        OffsetStart = FanOutCount * IdxOffsetSize
+        SHA1Start = OffsetStart + OffsetSize
+        EntrySize = OffsetSize + SHA1Size
+
+        def initialize(file)
+          if file =~ /\.idx$/
+            file = file[0...-3] + 'pack'
+          end
+
+          @name = file
+          @packfile = File.open(file)
+          @idxfile = File.open(file[0...-4]+'idx')
+          @idx = Mmap.new(@idxfile)
+
+          @offsets = [0]
+          FanOutCount.times do |i|
+            pos = @idx[i * IdxOffsetSize,IdxOffsetSize].unpack('N')[0]
+            if pos < @offsets[i]
+              raise PackFormatError, "pack #@name has discontinuous index #{i}"
+            end
+            @offsets << pos
+          end
+
+          @size = @offsets[-1]
+        end
+        
+        # given an index file, list out the shas that it's packfile contains
+        def self.get_shas(index_file)
+          @idxfile = File.open(index_file)
+          @idx = Mmap.new(@idxfile)
+          @offsets = [0]
+          FanOutCount.times do |i|
+            pos = @idx[i * IdxOffsetSize,IdxOffsetSize].unpack('N')[0]
+            if pos < @offsets[i]
+              raise PackFormatError, "pack #@name has discontinuous index #{i}"
+            end
+            @offsets << pos
+          end
+        
+          @size = @offsets[-1]
+          shas = []
+          
+          pos = SHA1Start
+          @size.times do
+            sha1 = @idx[pos,SHA1Size]
+            pos += EntrySize
+            shas << sha1.unpack("H*").first
+          end
+          shas
+        end
+
+        def name
+          @name
+        end
+        
+        def close
+          @packfile.close
+          @idx.unmap
+          @idxfile.close
+        end
+
+        def [](sha1)
+          offset = find_object(sha1)
+          return nil if !offset
+          return parse_object(offset)
+        end
+
+        def each_entry
+          pos = OffsetStart
+          @size.times do
+            offset = @idx[pos,OffsetSize].unpack('N')[0]
+            sha1 = @idx[pos+OffsetSize,SHA1Size]
+            pos += EntrySize
+            yield sha1, offset
+          end
+        end
+
+        def each_sha1
+          # unpacking the offset is quite expensive, so
+          # we avoid using #each
+          pos = SHA1Start
+          @size.times do
+            sha1 = @idx[pos,SHA1Size]
+            pos += EntrySize
+            yield sha1
+          end
+        end
+
+        def find_object(sha1)
+          slot = sha1[0]
+          return nil if !slot
+          first, last = @offsets[slot,2] 
+          while first < last
+            mid = (first + last) / 2
+            midsha1 = @idx[SHA1Start + mid * EntrySize,SHA1Size]
+            cmp = midsha1 <=> sha1
+
+            if cmp < 0
+              first = mid + 1
+            elsif cmp > 0
+              last = mid
+            else
+              pos = OffsetStart + mid * EntrySize
+              offset = @idx[pos,OffsetSize].unpack('N')[0]
+              return offset
+            end
+          end
+
+          nil
+        end
+        private :find_object
+
+        def parse_object(offset)
+          data, type = unpack_object(offset)
+          RawObject.new(OBJ_TYPES[type], data)
+        end
+        protected :parse_object
+
+        def unpack_object(offset)
+          obj_offset = offset
+          @packfile.seek(offset)
+
+          c = @packfile.read(1)[0]
+          size = c & 0xf
+          type = (c >> 4) & 7
+          shift = 4
+          offset += 1
+          while c & 0x80 != 0
+            c = @packfile.read(1)[0]
+            size |= ((c & 0x7f) << shift)
+            shift += 7
+            offset += 1
+          end
+
+          case type
+          when OBJ_OFS_DELTA, OBJ_REF_DELTA
+            data, type = unpack_deltified(type, offset, obj_offset, size)
+          when OBJ_COMMIT, OBJ_TREE, OBJ_BLOB, OBJ_TAG
+            data = unpack_compressed(offset, size)
+          else
+            raise PackFormatError, "invalid type #{type}"
+          end
+          [data, type]
+        end
+        private :unpack_object
+
+        def unpack_deltified(type, offset, obj_offset, size)
+          @packfile.seek(offset)
+          data = @packfile.read(SHA1Size)
+
+          if type == OBJ_OFS_DELTA
+            i = 0
+            c = data[i]
+            base_offset = c & 0x7f
+            while c & 0x80 != 0
+              c = data[i += 1]
+              base_offset += 1
+              base_offset <<= 7
+              base_offset |= c & 0x7f
+            end
+            base_offset = obj_offset - base_offset
+            offset += i + 1
+          else
+            base_offset = find_object(data)
+            offset += SHA1Size
+          end
+
+          base, type = unpack_object(base_offset)
+          delta = unpack_compressed(offset, size)
+          [patch_delta(base, delta), type]
+        end
+        private :unpack_deltified
+
+        def unpack_compressed(offset, destsize)
+          outdata = ""
+          @packfile.seek(offset)
+          zstr = Zlib::Inflate.new
+          while outdata.size < destsize
+            indata = @packfile.read(4096)
+            if indata.size == 0
+              raise PackFormatError, 'error reading pack data'
+            end
+            outdata += zstr.inflate(indata)
+          end
+          if outdata.size > destsize
+            raise PackFormatError, 'error reading pack data'
+          end
+          zstr.close
+          outdata
+        end
+        private :unpack_compressed
+
+        def patch_delta(base, delta)
+          src_size, pos = patch_delta_header_size(delta, 0)
+          if src_size != base.size
+            raise PackFormatError, 'invalid delta data'
+          end
+
+          dest_size, pos = patch_delta_header_size(delta, pos)
+          dest = ""
+          while pos < delta.size
+            c = delta[pos]
+            pos += 1
+            if c & 0x80 != 0
+              pos -= 1
+              cp_off = cp_size = 0
+              cp_off = delta[pos += 1] if c & 0x01 != 0
+              cp_off |= delta[pos += 1] << 8 if c & 0x02 != 0
+              cp_off |= delta[pos += 1] << 16 if c & 0x04 != 0
+              cp_off |= delta[pos += 1] << 24 if c & 0x08 != 0
+              cp_size = delta[pos += 1] if c & 0x10 != 0
+              cp_size |= delta[pos += 1] << 8 if c & 0x20 != 0
+              cp_size |= delta[pos += 1] << 16 if c & 0x40 != 0
+              cp_size = 0x10000 if cp_size == 0
+              pos += 1
+              dest += base[cp_off,cp_size]
+            elsif c != 0
+              dest += delta[pos,c]
+              pos += c
+            else
+              raise PackFormatError, 'invalid delta data'
+            end
+          end
+          dest
+        end
+        private :patch_delta
+
+        def patch_delta_header_size(delta, pos)
+          size = 0
+          shift = 0
+          begin
+            c = delta[pos]
+            if c == nil
+              raise PackFormatError, 'invalid delta header'
+            end
+            pos += 1
+            size |= (c & 0x7f) << shift
+            shift += 7
+          end while c & 0x80 != 0
+          [size, pos]
+        end
+        private :patch_delta_header_size
+      end
+    end
+  end 
+end

lib/grit/git-ruby/internal/raw_object.rb

@@ -0,0 +1,37 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#
+# provides native ruby access to git objects and pack files
+#
+
+require 'digest/sha1'
+
+module Grit 
+  module GitRuby 
+    module Internal
+      OBJ_NONE = 0
+      OBJ_COMMIT = 1
+      OBJ_TREE = 2
+      OBJ_BLOB = 3
+      OBJ_TAG = 4
+
+      OBJ_TYPES = [nil, :commit, :tree, :blob, :tag].freeze
+
+      class RawObject
+        attr_accessor :type, :content
+        def initialize(type, content)
+          @type = type
+          @content = content
+        end
+
+        def sha1
+          Digest::SHA1.digest("%s %d\0" % [@type, @content.length] + @content)
+        end
+      end
+    end 
+  end
+end

lib/grit/git-ruby/object.rb

@@ -0,0 +1,298 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#    Scott Chacon <schacon@gmail.com>
+#
+# provides native ruby access to git objects and pack files
+#
+
+# These classes translate the raw binary data kept in the sha encoded files
+# into parsed data that can then be used in another fashion
+
+module Grit
+  module GitRuby
+
+  # class for author/committer/tagger lines
+  class UserInfo
+    attr_accessor :name, :email, :date, :offset
+
+    def initialize(str)
+      m = /^(.*?) <(.*)> (\d+) ([+-])0*(\d+?)$/.match(str)
+      if !m
+        raise RuntimeError, "invalid %s header in commit" % str
+      end
+      @name = m[1]
+      @email = m[2]
+      @date = Time.at(Integer(m[3]))
+      @offset = (m[4] == "-" ? -1 : 1)*Integer(m[5])
+    end
+
+    def to_s
+      "%s <%s> %s %+05d" % [@name, @email, @date.to_i, @offset]
+    end
+  end
+
+  # base class for all git objects (blob, tree, commit, tag)
+  class Object
+    attr_accessor :repository
+
+    def Object.from_raw(rawobject, repository = nil)      
+      case rawobject.type
+      when :blob
+        return Blob.from_raw(rawobject, repository)
+      when :tree
+        return Tree.from_raw(rawobject, repository)
+      when :commit
+        return Commit.from_raw(rawobject, repository)
+      when :tag
+        return Tag.from_raw(rawobject, repository)
+      else
+        raise RuntimeError, "got invalid object-type"
+      end
+    end
+
+    def initialize
+      raise NotImplemented, "abstract class"
+    end
+
+    def type
+      raise NotImplemented, "abstract class"
+    end
+
+    def raw_content
+      raise NotImplemented, "abstract class"
+    end
+
+    def sha1
+      Digest::SHA1.hexdigest("%s %d\0" % \
+                             [self.type, self.raw_content.length] + \
+                             self.raw_content)
+    end
+  end
+
+  class Blob < Object
+    attr_accessor :content
+
+    def self.from_raw(rawobject, repository)
+      new(rawobject.content)
+    end
+
+    def initialize(content, repository=nil)
+      @content = content
+      @repository = repository
+    end
+
+    def type
+      :blob
+    end
+
+    def raw_content
+      @content
+    end
+  end
+
+  class DirectoryEntry
+    S_IFMT  = 00170000
+    S_IFLNK =  0120000
+    S_IFREG =  0100000
+    S_IFDIR =  0040000
+
+    attr_accessor :mode, :name, :sha1
+    def initialize(buf)
+      m = /^(\d+) (.*)\0(.{20})$/m.match(buf)
+      if !m
+        raise RuntimeError, "invalid directory entry"
+      end
+      @mode = 0
+      m[1].each_byte do |i|
+        @mode = (@mode << 3) | (i-'0'[0])
+      end
+      @name = m[2]
+      @sha1 = m[3].unpack("H*")[0]
+
+      if ![S_IFLNK, S_IFDIR, S_IFREG].include?(@mode & S_IFMT)
+        raise RuntimeError, "unknown type for directory entry"
+      end
+    end
+
+    def type
+      case @mode & S_IFMT
+      when S_IFLNK
+        @type = :link
+      when S_IFDIR
+        @type = :directory
+      when S_IFREG
+        @type = :file
+      else
+        raise RuntimeError, "unknown type for directory entry"
+      end
+    end
+
+    def type=(type)
+      case @type
+      when :link
+        @mode = (@mode & ~S_IFMT) | S_IFLNK
+      when :directory
+        @mode = (@mode & ~S_IFMT) | S_IFDIR
+      when :file
+        @mode = (@mode & ~S_IFMT) | S_IFREG
+      else
+        raise RuntimeError, "invalid type"
+      end
+    end
+
+    def format_type
+      case type
+      when :link
+        'link'
+      when :directory
+        'tree'
+      when :file
+        'blob'
+      end
+    end
+
+    def format_mode
+      "%06o" % @mode
+    end
+    
+    def raw
+      "%o %s\0%s" % [@mode, @name, [@sha1].pack("H*")]
+    end
+  end
+
+  class Tree < Object
+    attr_accessor :entry
+
+    def self.from_raw(rawobject, repository=nil)
+      entries = []
+      rawobject.content.scan(/\d+ .*?\0.{20}/m) do |raw|
+        entries << DirectoryEntry.new(raw)
+      end
+      new(entries, repository)
+    end
+
+    def initialize(entries=[], repository = nil)
+      @entry = entries
+      @repository = repository
+    end
+
+    def type
+      :tree
+    end
+
+    def raw_content
+      # TODO: sort correctly
+      #@entry.sort { |a,b| a.name <=> b.name }.
+      @entry.collect { |e| [[e.format_mode, e.format_type, e.sha1].join(' '), e.name].join("\t") }.join("\n")
+    end
+    
+    def actual_raw
+      #@entry.collect { |e| e.raw.join(' '), e.name].join("\t") }.join("\n")
+    end
+  end
+
+  class Commit < Object
+    attr_accessor :author, :committer, :tree, :parent, :message
+
+    def self.from_raw(rawobject, repository=nil)
+      parent = []
+      tree = author = committer = nil
+
+      headers, message = rawobject.content.split(/\n\n/, 2)
+      headers = headers.split(/\n/).map { |header| header.split(/ /, 2) }
+      headers.each do |key, value|
+        case key
+        when "tree"
+          tree = value
+        when "parent"
+          parent.push(value)
+        when "author"
+          author = UserInfo.new(value)
+        when "committer"
+          committer = UserInfo.new(value)
+        else
+          warn "unknown header '%s' in commit %s" % \
+            [key, rawobject.sha1.unpack("H*")[0]]
+        end
+      end
+      if not tree && author && committer
+        raise RuntimeError, "incomplete raw commit object"
+      end
+      new(tree, parent, author, committer, message, repository)
+    end
+
+    def initialize(tree, parent, author, committer, message, repository=nil)
+      @tree = tree
+      @author = author
+      @parent = parent
+      @committer = committer
+      @message = message
+      @repository = repository
+    end
+
+    def type
+      :commit
+    end
+
+    def raw_content
+      "tree %s\n%sauthor %s\ncommitter %s\n\n" % [
+        @tree,
+        @parent.collect { |i| "parent %s\n" % i }.join,
+        @author, @committer] + @message
+    end
+  end
+
+  class Tag < Object
+    attr_accessor :object, :type, :tag, :tagger, :message
+
+    def self.from_raw(rawobject, repository=nil)
+      headers, message = rawobject.content.split(/\n\n/, 2)
+      headers = headers.split(/\n/).map { |header| header.split(/ /, 2) }
+      headers.each do |key, value|
+        case key
+        when "object"
+          object = value
+        when "type"
+          if !["blob", "tree", "commit", "tag"].include?(value)
+            raise RuntimeError, "invalid type in tag"
+          end
+          type = value.to_sym
+        when "tag"
+          tag = value
+        when "tagger"
+          tagger = UserInfo.new(value)
+        else
+          warn "unknown header '%s' in tag" % \
+            [key, rawobject.sha1.unpack("H*")[0]]
+        end
+        if not object && type && tag && tagger
+          raise RuntimeError, "incomplete raw tag object"
+        end
+      end
+      new(object, type, tag, tagger, repository)
+    end
+
+    def initialize(object, type, tag, tagger, repository=nil)
+      @object = object
+      @type = type
+      @tag = tag
+      @tagger = tagger
+      @repository = repository
+    end
+
+    def raw_content
+      "object %s\ntype %s\ntag %s\ntagger %s\n\n" % \
+        [@object, @type, @tag, @tagger] + @message
+    end
+
+    def type
+      :tag
+    end
+  end
+
+  end
+end

lib/grit/git-ruby/repository.rb

@@ -0,0 +1,357 @@
+#
+# converted from the gitrb project
+#
+# authors: 
+#    Matthias Lederhofer <matled@gmx.net>
+#    Simon 'corecode' Schubert <corecode@fs.ei.tum.de>
+#    Scott Chacon <schacon@gmail.com>
+#
+# provides native ruby access to git objects and pack files
+#
+
+require 'grit/git-ruby/internal/raw_object'
+require 'grit/git-ruby/internal/pack'
+require 'grit/git-ruby/internal/loose'
+require 'grit/git-ruby/object'
+
+module Grit
+  module GitRuby
+    class Repository
+      
+      class NoSuchShaFound < StandardError
+      end
+      
+      attr_accessor :cache_ls_tree, :use_cache
+      
+      def initialize(git_dir, use_cache = false)
+        clear_cache()
+        @use_cache = use_cache
+        
+        @git_dir = git_dir
+      end
+      
+      def loose
+        @loose ||= Grit::GitRuby::Internal::LooseStorage.new(git_path("objects"))
+      end
+      
+      def packs
+        @packs ||= initpacks
+      end
+
+      def show
+        packs.each do |p|
+          puts p.name
+          puts
+          p.each_sha1 do |s|
+            puts "**#{p[s].type}**"
+            if p[s].type.to_s == 'commit'
+              puts s.unpack('H*')
+              puts p[s].content
+            end
+          end
+          puts
+        end
+      end
+
+      def object(sha)
+        o = get_raw_object_by_sha1(sha)
+        c = Grit::GitRuby::Object.from_raw(o)
+      end
+
+      def cat_file_type(sha)
+        get_raw_object_by_sha1(sha).type
+      end
+                  
+      def cat_file_size(sha)
+        get_raw_object_by_sha1(sha).content.size
+      end
+      
+      def cat_file(sha)
+        o = get_raw_object_by_sha1(sha)
+        object(sha).raw_content
+      end
+      
+      def log(sha, options = {})
+        @already_searched = {}
+        @use_cache = true
+        walk_log(sha, options)
+      end
+
+      def walk_log(sha, opts)
+        return [] if @already_searched[sha] # to prevent rechecking branches
+        @already_searched[sha] = true
+        
+        array = []          
+        if (sha)
+          o = get_raw_object_by_sha1(sha)
+          c = Grit::GitRuby::Object.from_raw(o)
+
+          add_sha = true
+          
+          if opts[:since] && opts[:since].is_a?(Time) && (opts[:since] > c.committer.date)
+            add_sha = false
+          end
+          if opts[:until] && opts[:until].is_a?(Time) && (opts[:until] < c.committer.date)
+            add_sha = false
+          end
+          
+          # follow all parents unless '--first-parent' is specified #
+          subarray = []
+          
+          if !c.parent.first && opts[:path_limiter]  # check for the last commit
+            add_sha = false
+          end
+          
+          c.parent.each do |psha|
+            if psha && !files_changed?(c.tree, object(psha).tree, opts[:path_limiter])
+              add_sha = false 
+            end
+            subarray += walk_log(psha, opts) 
+            next if opts[:first_parent]
+          end
+          
+          if (!opts[:max_count] || (array.size < opts[:max_count]))
+            if add_sha
+              output = "commit #{sha}\n"
+              output += o.content + "\n\n"
+              array << [sha, output]
+            end          
+            array += subarray
+          end
+                                
+        end
+        
+        array
+      end
+      
+      # returns true if the files in path_limiter were changed, or no path limiter
+      def files_changed?(tree_sha1, tree_sha2, path_limiter = nil)
+        if path_limiter
+          mod = quick_diff(tree_sha1, tree_sha2)
+          files = mod.map { |c| c.first }
+          path_limiter.to_a.each do |filepath|
+            if files.include?(filepath)
+              return true
+            end
+          end
+          return false
+        end
+        true
+      end
+      
+      def last_commits(commit_sha, looking_for)        
+        # swap caching temporarily - we have to do this because the algorithm 
+        # that dumb scott used ls-tree's each tree twice, which is 90% of the
+        # time this takes, so caching those hits halves the time this takes to run
+        # but, it does take up memory, so if you don't want it, i clear it later
+        old_use_cache = @use_cache 
+        @use_cache = true
+
+          @already_searched = {}
+          data = look_for_commits(commit_sha, looking_for)
+
+        @use_cache = old_use_cache
+        clear_cache if !old_use_cache 
+
+        data
+      end
+    
+      def clear_cache
+        @cache_ls_tree = {}
+      end
+      
+      def look_for_commits(commit_sha, looking_for)        
+        return [] if @already_searched[commit_sha] # to prevent rechecking branches
+        @already_searched[commit_sha] = true
+        
+        commit = object(commit_sha)
+        tree_sha = commit.tree
+        
+        found_data = []
+        
+        # at the beginning of the branch
+        if commit.parent.size == 0  
+          looking_for.each do |search|
+            # prevents the rare case of multiple branch starting points with 
+            # files that have never changed
+            if found_data.assoc(search) 
+              found_data << [search, commit_sha]
+            end
+          end
+          return found_data
+        end
+        
+        # go through the parents recursively, looking for somewhere this has been changed
+        commit.parent.each do |pc|
+          diff = quick_diff(tree_sha, object(pc).tree, '.', false)
+          
+          # remove anything found
+          looking_for.each do |search|
+            if match = diff.assoc(search)
+              found_data << [search, commit_sha, match]
+              looking_for.delete(search)
+            end
+          end
+          
+          if looking_for.size <= 0  # we're done
+            return found_data
+          end
+
+          found_data += look_for_commits(pc, looking_for)  # recurse into parent
+        end
+        
+        ## TODO : find most recent commit with change in any parent
+        found_data
+      end
+            
+      def quick_diff(tree1, tree2, path = '.', recurse = true)
+        # handle empty trees
+        changed = []
+
+        t1 = ls_tree(tree1) if tree1
+        t2 = ls_tree(tree2) if tree2
+
+        # finding files that are different
+        t1['blob'].each do |file, hsh|
+          t2_file = t2['blob'][file] rescue nil
+          full = File.join(path, file)
+          if !t2_file
+            changed << [full, 'added', hsh[:sha], nil]      # not in parent
+          elsif (hsh[:sha] != t2_file[:sha])
+            changed << [full, 'modified', hsh[:sha], t2_file[:sha]]   # file changed
+          end
+        end if t1
+        t2['blob'].each do |file, hsh|
+          if !t1['blob'][file]
+            changed << [File.join(path, file), 'removed', nil, hsh[:sha]]
+          end if t1
+        end if t2
+
+        t1['tree'].each do |dir, hsh|
+          t2_tree = t2['tree'][dir] rescue nil
+          full = File.join(path, dir)
+          if !t2_tree
+            if recurse
+              changed += quick_diff(hsh[:sha], nil, full) 
+            else
+              changed << [full, 'added', hsh[:sha], nil]      # not in parent
+            end
+          elsif (hsh[:sha] != t2_tree[:sha])
+            if recurse
+              changed += quick_diff(hsh[:sha], t2_tree[:sha], full) 
+            else
+              changed << [full, 'modified', hsh[:sha], t2_tree[:sha]]   # file changed
+            end
+          end
+        end if t1
+        t2['tree'].each do |dir, hsh|
+          t1_tree = t2['tree'][dir] rescue nil
+          full = File.join(path, dir)
+          if !t1_tree
+            if recurse
+              changed += quick_diff(nil, hsh[:sha], full) 
+            else
+              changed << [full, 'removed', nil, hsh[:sha]]
+            end
+          end
+        end if t2
+
+        changed
+      end
+      
+      def ls_tree(sha)
+        return @cache_ls_tree[sha] if @cache_ls_tree[sha] && @use_cache
+        
+        data = {'blob' => {}, 'tree' => {}}
+        self.object(sha).entry.each do |e|
+          data[e.format_type][e.name] = {:mode => e.format_mode, :sha => e.sha1}
+        end 
+        @cache_ls_tree[sha] = data             
+      end
+            
+      def get_object_by_sha1(sha1)
+        r = get_raw_object_by_sha1(sha1)
+        return nil if !r
+        Object.from_raw(r, self)
+      end
+      
+      def put_raw_object(content, type)
+        loose.put_raw_object(content, type)
+      end
+      
+      def object_exists?(sha1)
+        sha_hex = [sha1].pack("H*")
+        return true if in_packs?(sha_hex)
+        return true if in_loose?(sha_hex)
+        initpacks
+        return true if in_packs?(sha_hex) #maybe the object got packed in the meantime
+        false
+      end
+      
+      def in_packs?(sha_hex)
+        # try packs
+        packs.each do |pack|
+          return true if pack[sha_hex]
+        end
+        false
+      end
+      
+      def in_loose?(sha_hex)
+        return true if loose[sha_hex]
+        false
+      end
+      
+      def get_raw_object_by_sha1(sha1)
+        sha1 = [sha1].pack("H*")
+        
+        # try packs
+        packs.each do |pack|
+          o = pack[sha1]
+          return o if o
+        end
+        
+        # try loose storage
+        o = loose[sha1]
+        return o if o
+
+        # try packs again, maybe the object got packed in the meantime
+        initpacks
+        packs.each do |pack|
+          o = pack[sha1]
+          return o if o
+        end
+
+        raise NoSuchShaFound
+      end
+
+      protected
+      
+        def git_path(path)
+          return "#@git_dir/#{path}"
+        end
+
+      private 
+      
+        def initpacks
+          @packs.each do |pack|
+            pack.close
+          end if @packs
+          
+          @packs = []
+          if File.exists?(git_path("objects/pack"))
+            Dir.open(git_path("objects/pack/")) do |dir|
+              dir.each do |entry|
+                if entry =~ /\.pack$/i
+                  @packs << Grit::GitRuby::Internal::PackStorage.new(git_path("objects/pack/" \
+                                                                    + entry))
+                end
+              end
+            end
+          end
+          @packs
+        end
+      
+    end
+    
+  end
+end

lib/grit/git.rb

@@ -8,6 +8,8 @@ end
 module Grit
   
   class Git
+    include Grit::GitRuby
+    
     class GitTimeout < RuntimeError
       attr_reader :command, :bytes_read
 
@@ -27,7 +29,7 @@ module Grit
     self.git_timeout = 5
     
     attr_accessor :git_dir, :bytes_read
-    
+
     def initialize(git_dir)
       self.git_dir    = git_dir
       self.bytes_read = 0
@@ -61,6 +63,8 @@ module Grit
       response
     end
 
+    
+    
     def sh(command)
       pid, _, io, _ = Open4.popen4(command)
       ret = Timeout.timeout(self.class.git_timeout) { io.read }

test/fixtures/cat_file_blob_ruby

@@ -0,0 +1,5 @@
+== 0.7.0 / 2008-01-07
+
+* 1 major enhancement
+  * First public release!
+

test/fixtures/cat_file_commit_ruby

@@ -0,0 +1,7 @@
+tree 77fc9894c0904279fde93adc9c0ba231515ce68a
+parent 30e367cef2203eba2b341dc9050993b06fd1e108
+parent 420eac97a826bfac8724b6b0eef35c20922124b7
+author Tom Preston-Werner <tom@mojombo.com> 1208054148 -0700
+committer Tom Preston-Werner <tom@mojombo.com> 1208054148 -0700
+
+Merge branch 'master' of git://github.com/dustin/grit

test/fixtures/cat_file_tree_ruby

@@ -0,0 +1,7 @@
+100644 blob baaa47163a922b716898936f4ab032db4e08ae8a	.gitignore
+100644 blob 4232d073306f01cf0b895864e5a5cfad7dd76fce	History.txt
+100644 blob 22158f1075113476d332d6f5112cf948f38ae658	Manifest.txt
+100644 blob dd53bb4983125be6a5b2cc7ac9e89d75804a6a73	README.txt
+100644 blob fdbea19c6688404f2a65767d8f889a0acdb0b25a	Rakefile
+040000 tree a93f4c338734259d8ae577b16537ad6b99a90937	lib
+040000 tree ce9b0e78f28d705665030d29d72515f86c28b2b3	test

test/test_rubygit.rb

@@ -0,0 +1,41 @@
+require File.dirname(__FILE__) + '/helper'
+
+class TestRubyGit < Test::Unit::TestCase
+  
+  def setup
+    @git = Git.new(File.join(File.dirname(__FILE__), *%w[dot_git]))
+    @commit_sha = '5e3ee1198672257164ce3fe31dea3e40848e68d5'
+    @tree_sha = 'cd7422af5a2e0fff3e94d6fb1a8fff03b2841881'
+    @blob_sha = '4232d073306f01cf0b895864e5a5cfad7dd76fce'
+  end
+
+  def test_cat_file_contents_commit
+    out = @git.cat_file({:p => true}, @commit_sha)
+    assert_equal out, fixture('cat_file_commit_ruby')
+  end
+
+  def test_cat_file_contents_tree
+    out = @git.cat_file({:p => true}, @tree_sha)
+    assert_equal out, fixture('cat_file_tree_ruby').chomp
+  end
+
+  def test_cat_file_contents_blob
+    out = @git.cat_file({:p => true}, @blob_sha)
+    assert_equal out, fixture('cat_file_blob_ruby')
+  end
+
+  def test_cat_file_size
+    out = @git.cat_file({:s => true}, @tree_sha)
+    assert_equal '252', out
+  end
+  
+  def test_file_type
+    out = @git.file_type(@tree_sha).to_s
+    assert_equal 'tree', out
+    out = @git.file_type(@blob_sha).to_s
+    assert_equal 'blob', out
+    out = @git.file_type(@commit_sha).to_s
+    assert_equal 'commit', out
+  end
+  
+end