chunk_cache
bandstore
dedupestore => dds
init command


TODO
----
* Remote stores
* Stat and chunk cache

DONE
----
* Encryption
* Hard links
* cache redesign
* Symbolic links
* Owner, group, mode, ctime, mtime

cache = Cache(path,)

for file in files:
    chunks = chunkify(file)
    for chunk in chunkify(file):
        if chunk.sha in cache:
    	    cache.chunk_inc_ref(chunk)
		else:
		    fs.add_chunk(chunk)
		
	entry = Entry
    archive.add(entry)
Repository layout
-----------------
REPO/README
REPO/VERSION
REPO/tid = x
REPO/data/
REPO/txn-active/tid
REPO/txn-active/add/<PATH>/
REPO/txn-active/delete/<PATH>/
REPO/txn-active/tid
REPO/txn-commit/add/<PATH>/
REPO/txn-commit/delete/<PATH>/

REPO/archives/<ARCHIVENAME>
REPO/blocks/XX/YY/XYZ

txn_completed/add/<PATH>/
txn_completed/delete/<PATH>/

API
---
"""
class Cache(object):

	def chunk_inc_ref(self, chunk):
		self.chunk_refcount.setdefault(chunk.sha, 0)
		self.chunk_refcount[chunk.sha] += 1

	def chunk_dec_ref(self, chunk):
		assert self.chunk_refcount.get(chunk.sha, 0) > 0
		self.chunk_refcount[chunk.sha] -= 1
		if self.chunk_refcount[chunk.sha] == 0:
			self.fs.delete_chunk(self.sha)

txn = txn_begin()