WIP
Add some convenient functions to the API
Import (broken) tests from irminsule
Add missing file
Fix stupid mistake in Git.find

All test pass.
Refactoring with SHA1 keys
Refactoring in tests
Fix some doc messages
Fix a small race in recursive mkdir
Remove debug statements in Git.find
Minor API updates
Simplify and add more tests
SERIALIZABLE API changes
Fix the type representation for tags
Fix (again) the race with recursive Lwt_unix.mkdir
Add (broken) tests for tags
Implement input/output for tags

This commit fixes the tests.
More complete (and correct) API for references
Add a (working) test for references
Add tests for list and type_of