add initial README file

README.txt

+libgit2 - the Git linkable library
+==================================
+
+libgit2 is a portable, pure C implementation of the Git core methods provided as a
+re-entrant linkable library with a solid API, allowing you to write native
+speed custom Git applications in any language with bindings.
+
+
+Why Do We Need It
+==================================
+
+In the current Git project, though a libgit.a file is produced it is
+not re-entrant (it will call <code>die()</code> on basically any error)
+and it has no stable or well-designed public API.  As there is no good
+way to link to this effectively, a new library was needed that fulfilled
+these requirements.  Thus libgit2.
+
+Though it would be nice to use the same library that Git itself uses, 
+Git actually has a pretty simple storage format and just having native
+access to that is pretty useful.  Eventually we would like to have most
+of the functionality of the core Git tools or even get the library
+integrated into Git itself, but in the meantime having a cleanly designed
+and maintained linkable Git library with a public API will likely be helpful
+to lots of people.
+
+What It Can Do
+==================================
+
+libgit2 is already very usable.
+* raw <-> hex SHA conversions
+* raw object reading (loose and packed)
+* raw object writing (loose)
+* revlist walker
+* commit, tag and tree object parsing and write-back
+* tree traversal
+* basic index file (staging area) operations
+
+
+Installing libgit2
+==================================
+
+ $ git clone git://github.com/libgit2/libgit2.git
+ $ cd libgit2
+ $ make
+ $ make install
+
+That should get it installed on Mac, Linux or Windows.
+Once that is done, you should be able to link the library to your program
+with a normal "-lgit2".
+
+Language Bindings
+==================================
+
+So you want to use Git from your favorite programming language.  Here are
+the bindings to libgit2 that are currently available:
+
+== Ruby ==
+
+Ribbit is the reference library used to make sure the 
+libgit2 API is sane.  This should be mostly up to date.
+
+http://github.com/libgit2/ribbit
+
+
+== Erlang ==
+
+Geef is an example of an Erlang NIF binding to libgit2.  A bit out of 
+date, but basically works.  Best as a proof of concept of what you could
+do with Erlang and NIFs with libgit2.
+
+http://github.com/schacon/geef
+
+
+If you start another language binding to libgit2, please let us know so
+we can add it to the list.
+
+License 
+==================================
+libgit2 is under GPL2 with linking exemption, which basically means you
+can link to the library with any program, commercial, open source or
+other.  However, you cannot modify libgit2 and distribute it without
+supplying the source.
+
+See the COPYING file for the full license text.