very simple content tracker

bkk.py

#!/usr/bin/env python
import sys
import os
import dbm
import json
import uuid

print("BaKKit up")
try:
    op = sys.argv[1]
except IndexError:
    print ("please specify op")
    sys.exit()
try:
    repo_dir = sys.argv[2]
    if repo_dir[-1] != "/":
        repo_dir += "/"
except IndexError:
    print ("please specify root folder")
    sys.exit()

location = lambda x: os.path.join(repo_dir, x)

if op == "init":
    try:
        os.unlink(location(".bkkdb"))
    except FileNotFoundError:
        pass
    db = dbm.open(location(".bkkdb"), 'c')
    db['root'] = json.dumps({'tree': {}, 'parent': None})
    db['head'] = "root"
    db.close()
    sys.exit()

db = dbm.open(location(".bkkdb"), 'w')

# db structures:
# commit_id -> {'msg': commit msg, 'tree': {'path': blob_id}, 'parent': parent commit_id}
# blob_id -> content
# "head" links to last commit id
# "root" is the first commit, also has no parent

def read_commit(blob_id):
    return json.loads(db[blob_id].decode("utf8"))

if op == "log" or op == "longlog":
    commit = read_commit(db['head'])
    counter = 0
    while commit['parent']:
        print("%d) %s" % (counter, commit['msg']))
        if op == "longlog":
            for fname, blob_id in commit['tree'].items():
                print("filename %s -- content:" % fname)
                print(db[blob_id])
        counter -= 1
        commit = read_commit(commit['parent'])

if op == "commit":
    newcontent = {}
    for root, dirs, files in os.walk(repo_dir):
        for name in files:
            if name.startswith("."):
                break
            f = os.path.join(root[len(repo_dir):], name)
            with open(location(f), 'r') as fd:
                newcontent[f] = fd.read()

    lastcontent = {}
    lasttree = read_commit(db['head'])['tree']
    for path, blob_key in lasttree.items():
        lastcontent[path] = db[blob_key].decode("utf8")

    if lastcontent != newcontent:
        print("write commit msg")
        msg = input()

        new_tree_obj = {}
        for path, newcontent in newcontent.items():
            if newcontent != lastcontent.get(path):
                # if the file changed or new, re-add the whole file
                newkey = uuid.uuid4().hex
                db[newkey] = newcontent
                new_tree_obj[path] = newkey
            else:
                new_tree_obj[path] = lasttree[path]

        newkey = uuid.uuid4().hex
        dbval = json.dumps({'msg': msg, 'tree': new_tree_obj, 'parent': db['head'].decode("utf8")})
        print("storing %s in %s" % (dbval, newkey))
        db[newkey] = dbval
        db['head'] = newkey


db.close()