]> arthur.barton.de Git - bup.git/blobdiff - lib/bup/git.py
Move bloom-related stuff from git.py to a new bloom.py.
[bup.git] / lib / bup / git.py
index 5ec94ebfa3f3c1f85705fc72e47ac24e723e3446..f3774bcd12829cc7c8e218b94c5b403228c4cb3b 100644 (file)
@@ -2,10 +2,12 @@
 bup repositories are in Git format. This library allows us to
 interact with the Git data structures.
 """
-import os, zlib, time, subprocess, struct, stat, re, tempfile
-import heapq
+import os, sys, zlib, time, subprocess, struct, stat, re, tempfile, glob
 from bup.helpers import *
-from bup import _helpers
+from bup import _helpers, path, bloom
+
+MIDX_VERSION = 4
+SEEK_END=2  # os.SEEK_END is not defined in python 2.4
 
 verbose = 0
 ignore_midx = 0
@@ -37,6 +39,46 @@ def repo(sub = ''):
     return os.path.join(repodir, sub)
 
 
+def repo_rel(path):
+    full = os.path.abspath(path)
+    fullrepo = os.path.abspath(repo(''))
+    if not fullrepo.endswith('/'):
+        fullrepo += '/'
+    if full.startswith(fullrepo):
+        path = full[len(fullrepo):]
+    if path.startswith('index-cache/'):
+        path = path[len('index-cache/'):]
+    return path
+
+
+def all_packdirs():
+    paths = [repo('objects/pack')]
+    paths += glob.glob(repo('index-cache/*/.'))
+    return paths
+
+
+def auto_midx(objdir):
+    args = [path.exe(), 'midx', '--auto', '--dir', objdir]
+    try:
+        rv = subprocess.call(args, stdout=open('/dev/null', 'w'))
+    except OSError, e:
+        # make sure 'args' gets printed to help with debugging
+        add_error('%r: exception: %s' % (args, e))
+        raise
+    if rv:
+        add_error('%r: returned %d' % (args, rv))
+
+    args = [path.exe(), 'bloom', '--dir', objdir]
+    try:
+        rv = subprocess.call(args, stdout=open('/dev/null', 'w'))
+    except OSError, e:
+        # make sure 'args' gets printed to help with debugging
+        add_error('%r: exception: %s' % (args, e))
+        raise
+    if rv:
+        add_error('%r: returned %d' % (args, rv))
+
+
 def mangle_name(name, mode, gitmode):
     """Mangle a file name to present an abstract name for segmented files.
     Mangled file names will have the ".bup" extension added to them. If a
@@ -128,28 +170,24 @@ def _decode_packobj(buf):
 
 
 class PackIdx:
-    """Object representation of a Git pack index file."""
-    def __init__(self, filename):
-        self.name = filename
-        self.map = mmap_read(open(filename))
-        assert(str(self.map[0:8]) == '\377tOc\0\0\0\2')
-        self.fanout = list(struct.unpack('!256I',
-                                         str(buffer(self.map, 8, 256*4))))
-        self.fanout.append(0)  # entry "-1"
-        nsha = self.fanout[255]
-        self.ofstable = buffer(self.map,
-                               8 + 256*4 + nsha*20 + nsha*4,
-                               nsha*4)
-        self.ofs64table = buffer(self.map,
-                                 8 + 256*4 + nsha*20 + nsha*4 + nsha*4)
+    def __init__(self):
+        assert(0)
 
-    def _ofs_from_idx(self, idx):
-        ofs = struct.unpack('!I', str(buffer(self.ofstable, idx*4, 4)))[0]
-        if ofs & 0x80000000:
-            idx64 = ofs & 0x7fffffff
-            ofs = struct.unpack('!I',
-                                str(buffer(self.ofs64table, idx64*8, 8)))[0]
-        return ofs
+    def find_offset(self, hash):
+        """Get the offset of an object inside the index file."""
+        idx = self._idx_from_hash(hash)
+        if idx != None:
+            return self._ofs_from_idx(idx)
+        return None
+
+    def exists(self, hash, want_source=False):
+        """Return nonempty if the object exists in this index."""
+        if hash and (self._idx_from_hash(hash) != None):
+            return want_source and os.path.basename(self.name) or True
+        return None
+
+    def __len__(self):
+        return int(self.fanout[255])
 
     def _idx_from_hash(self, hash):
         global _total_searches, _total_steps
@@ -158,13 +196,12 @@ class PackIdx:
         b1 = ord(hash[0])
         start = self.fanout[b1-1] # range -1..254
         end = self.fanout[b1] # range 0..255
-        buf = buffer(self.map, 8 + 256*4, end*20)
         want = str(hash)
         _total_steps += 1  # lookup table is a step
         while start < end:
             _total_steps += 1
             mid = start + (end-start)/2
-            v = str(buf[mid*20:(mid+1)*20])
+            v = self._idx_to_hash(mid)
             if v < want:
                 start = mid+1
             elif v > want:
@@ -173,32 +210,67 @@ class PackIdx:
                 return mid
         return None
 
-    def find_offset(self, hash):
-        """Get the offset of an object inside the index file."""
-        idx = self._idx_from_hash(hash)
-        if idx != None:
-            return self._ofs_from_idx(idx)
-        return None
 
-    def exists(self, hash):
-        """Return nonempty if the object exists in this index."""
-        return hash and (self._idx_from_hash(hash) != None) and True or None
+class PackIdxV1(PackIdx):
+    """Object representation of a Git pack index (version 1) file."""
+    def __init__(self, filename, f):
+        self.name = filename
+        self.idxnames = [self.name]
+        self.map = mmap_read(f)
+        self.fanout = list(struct.unpack('!256I',
+                                         str(buffer(self.map, 0, 256*4))))
+        self.fanout.append(0)  # entry "-1"
+        nsha = self.fanout[255]
+        self.sha_ofs = 256*4
+        self.shatable = buffer(self.map, self.sha_ofs, nsha*24)
+
+    def _ofs_from_idx(self, idx):
+        return struct.unpack('!I', str(self.shatable[idx*24 : idx*24+4]))[0]
+
+    def _idx_to_hash(self, idx):
+        return str(self.shatable[idx*24+4 : idx*24+24])
 
     def __iter__(self):
         for i in xrange(self.fanout[255]):
-            yield buffer(self.map, 8 + 256*4 + 20*i, 20)
+            yield buffer(self.map, 256*4 + 24*i + 4, 20)
 
-    def __len__(self):
-        return int(self.fanout[255])
 
+class PackIdxV2(PackIdx):
+    """Object representation of a Git pack index (version 2) file."""
+    def __init__(self, filename, f):
+        self.name = filename
+        self.idxnames = [self.name]
+        self.map = mmap_read(f)
+        assert(str(self.map[0:8]) == '\377tOc\0\0\0\2')
+        self.fanout = list(struct.unpack('!256I',
+                                         str(buffer(self.map, 8, 256*4))))
+        self.fanout.append(0)  # entry "-1"
+        nsha = self.fanout[255]
+        self.sha_ofs = 8 + 256*4
+        self.shatable = buffer(self.map, self.sha_ofs, nsha*20)
+        self.ofstable = buffer(self.map,
+                               self.sha_ofs + nsha*20 + nsha*4,
+                               nsha*4)
+        self.ofs64table = buffer(self.map,
+                                 8 + 256*4 + nsha*20 + nsha*4 + nsha*4)
+
+    def _ofs_from_idx(self, idx):
+        ofs = struct.unpack('!I', str(buffer(self.ofstable, idx*4, 4)))[0]
+        if ofs & 0x80000000:
+            idx64 = ofs & 0x7fffffff
+            ofs = struct.unpack('!Q',
+                                str(buffer(self.ofs64table, idx64*8, 8)))[0]
+        return ofs
+
+    def _idx_to_hash(self, idx):
+        return str(self.shatable[idx*20:(idx+1)*20])
+
+    def __iter__(self):
+        for i in xrange(self.fanout[255]):
+            yield buffer(self.map, 8 + 256*4 + 20*i, 20)
 
-def extract_bits(buf, nbits):
-    """Take the first 'nbits' bits from 'buf' and return them as an integer."""
-    mask = (1<<nbits) - 1
-    v = _helpers.firstword(buf)
-    v = (v >> (32-nbits)) & mask
-    return v
 
+extract_bits = _helpers.extract_bits
 
 class PackMidx:
     """Wrapper which contains data from multiple index files.
@@ -208,24 +280,41 @@ class PackMidx:
     """
     def __init__(self, filename):
         self.name = filename
+        self.force_keep = False
         assert(filename.endswith('.midx'))
         self.map = mmap_read(open(filename))
-        if str(self.map[0:8]) == 'MIDX\0\0\0\1':
-            log('Warning: ignoring old-style midx %r\n' % filename)
-            self.bits = 0
-            self.entries = 1
-            self.fanout = buffer('\0\0\0\0')
-            self.shalist = buffer('\0'*20)
-            self.idxnames = []
-        else:
-            assert(str(self.map[0:8]) == 'MIDX\0\0\0\2')
-            self.bits = _helpers.firstword(self.map[8:12])
-            self.entries = 2**self.bits
-            self.fanout = buffer(self.map, 12, self.entries*4)
-            shaofs = 12 + self.entries*4
-            nsha = self._fanget(self.entries-1)
-            self.shalist = buffer(self.map, shaofs, nsha*20)
-            self.idxnames = str(self.map[shaofs + 20*nsha:]).split('\0')
+        if str(self.map[0:4]) != 'MIDX':
+            log('Warning: skipping: invalid MIDX header in %r\n' % filename)
+            self.force_keep = True
+            return self._init_failed()
+        ver = struct.unpack('!I', self.map[4:8])[0]
+        if ver < MIDX_VERSION:
+            log('Warning: ignoring old-style (v%d) midx %r\n' 
+                % (ver, filename))
+            self.force_keep = False  # old stuff is boring  
+            return self._init_failed()
+        if ver > MIDX_VERSION:
+            log('Warning: ignoring too-new (v%d) midx %r\n'
+                % (ver, filename))
+            self.force_keep = True  # new stuff is exciting
+            return self._init_failed()
+
+        self.bits = _helpers.firstword(self.map[8:12])
+        self.entries = 2**self.bits
+        self.fanout = buffer(self.map, 12, self.entries*4)
+        self.sha_ofs = 12 + self.entries*4
+        self.nsha = nsha = self._fanget(self.entries-1)
+        self.shatable = buffer(self.map, self.sha_ofs, nsha*20)
+        self.which_ofs = self.sha_ofs + 20*nsha
+        self.whichlist = buffer(self.map, self.which_ofs, nsha*4)
+        self.idxnames = str(self.map[self.which_ofs + 4*nsha:]).split('\0')
+
+    def _init_failed(self):
+        self.bits = 0
+        self.entries = 1
+        self.fanout = buffer('\0\0\0\0')
+        self.shatable = buffer('\0'*20)
+        self.idxnames = []
 
     def _fanget(self, i):
         start = i*4
@@ -233,9 +322,15 @@ class PackMidx:
         return _helpers.firstword(s)
 
     def _get(self, i):
-        return str(self.shalist[i*20:(i+1)*20])
+        return str(self.shatable[i*20:(i+1)*20])
+
+    def _get_idx_i(self, i):
+        return struct.unpack('!I', self.whichlist[i*4:(i+1)*4])[0]
+
+    def _get_idxname(self, i):
+        return self.idxnames[self._get_idx_i(i)]
 
-    def exists(self, hash):
+    def exists(self, hash, want_source=False):
         """Return nonempty if the object exists in the index files."""
         global _total_searches, _total_steps
         _total_searches += 1
@@ -266,12 +361,12 @@ class PackMidx:
                 end = mid
                 endv = _helpers.firstword(v)
             else: # got it!
-                return True
+                return want_source and self._get_idxname(mid) or True
         return None
 
     def __iter__(self):
         for i in xrange(self._fanget(self.entries-1)):
-            yield buffer(self.shalist, i*20, 20)
+            yield buffer(self.shatable, i*20, 20)
 
     def __len__(self):
         return int(self._fanget(self.entries-1))
@@ -284,8 +379,10 @@ class PackIdxList:
         assert(_mpi_count == 0) # these things suck tons of VM; don't waste it
         _mpi_count += 1
         self.dir = dir
-        self.also = {}
+        self.also = set()
         self.packs = []
+        self.do_bloom = False
+        self.bloom = None
         self.refresh()
 
     def __del__(self):
@@ -299,19 +396,27 @@ class PackIdxList:
     def __len__(self):
         return sum(len(pack) for pack in self.packs)
 
-    def exists(self, hash):
+    def exists(self, hash, want_source=False):
         """Return nonempty if the object exists in the index files."""
         global _total_searches
         _total_searches += 1
         if hash in self.also:
             return True
-        for i in range(len(self.packs)):
+        if self.do_bloom and self.bloom is not None:
+            _total_searches -= 1  # will be incremented by bloom
+            if self.bloom.exists(hash):
+                self.do_bloom = False
+            else:
+                return None
+        for i in xrange(len(self.packs)):
             p = self.packs[i]
             _total_searches -= 1  # will be incremented by sub-pack
-            if p.exists(hash):
+            ix = p.exists(hash, want_source=want_source)
+            if ix:
                 # reorder so most recently used packs are searched first
                 self.packs = [p] + self.packs[:i] + self.packs[i+1:]
-                return p.name
+                return ix
+        self.do_bloom = True
         return None
 
     def refresh(self, skip_midx = False):
@@ -326,6 +431,8 @@ class PackIdxList:
         The module-global variable 'ignore_midx' can force this function to
         always act as if skip_midx was True.
         """
+        self.bloom = None # Always reopen the bloom as it may have been relaced
+        self.do_bloom = False
         skip_midx = skip_midx or ignore_midx
         d = dict((p.name, p) for p in self.packs
                  if not skip_midx or not isinstance(p, PackMidx))
@@ -336,51 +443,61 @@ class PackIdxList:
                     if isinstance(ix, PackMidx):
                         for name in ix.idxnames:
                             d[os.path.join(self.dir, name)] = ix
-                for f in os.listdir(self.dir):
-                    full = os.path.join(self.dir, f)
-                    if f.endswith('.midx') and not d.get(full):
+                for full in glob.glob(os.path.join(self.dir,'*.midx')):
+                    if not d.get(full):
                         mx = PackMidx(full)
                         (mxd, mxf) = os.path.split(mx.name)
-                        broken = 0
+                        broken = False
                         for n in mx.idxnames:
                             if not os.path.exists(os.path.join(mxd, n)):
                                 log(('warning: index %s missing\n' +
                                     '  used by %s\n') % (n, mxf))
-                                broken += 1
-                        if not broken:
+                                broken = True
+                        if broken:
+                            del mx
+                            unlink(full)
+                        else:
                             midxl.append(mx)
                 midxl.sort(lambda x,y: -cmp(len(x),len(y)))
                 for ix in midxl:
-                    any = 0
+                    any_needed = False
                     for sub in ix.idxnames:
                         found = d.get(os.path.join(self.dir, sub))
                         if not found or isinstance(found, PackIdx):
                             # doesn't exist, or exists but not in a midx
-                            d[ix.name] = ix
-                            for name in ix.idxnames:
-                                d[os.path.join(self.dir, name)] = ix
-                            any += 1
+                            any_needed = True
                             break
-                    if not any:
-                        log('midx: removing redundant: %s\n'
-                            % os.path.basename(ix.name))
+                    if any_needed:
+                        d[ix.name] = ix
+                        for name in ix.idxnames:
+                            d[os.path.join(self.dir, name)] = ix
+                    elif not ix.force_keep:
+                        debug1('midx: removing redundant: %s\n'
+                               % os.path.basename(ix.name))
                         unlink(ix.name)
-            for f in os.listdir(self.dir):
-                full = os.path.join(self.dir, f)
-                if f.endswith('.idx') and not d.get(full):
-                    ix = PackIdx(full)
+            for full in glob.glob(os.path.join(self.dir,'*.idx')):
+                if not d.get(full):
+                    try:
+                        ix = open_idx(full)
+                    except GitError, e:
+                        add_error(e)
+                        continue
                     d[full] = ix
+            bfull = os.path.join(self.dir, 'bup.bloom')
+            if self.bloom is None and os.path.exists(bfull):
+                self.bloom = bloom.ShaBloom(bfull)
             self.packs = list(set(d.values()))
-        log('PackIdxList: using %d index%s.\n'
+            self.packs.sort(lambda x,y: -cmp(len(x),len(y)))
+            if self.bloom and self.bloom.valid() and len(self.bloom) >= len(self):
+                self.do_bloom = True
+            else:
+                self.bloom = None
+        debug1('PackIdxList: using %d index%s.\n'
             % (len(self.packs), len(self.packs)!=1 and 'es' or ''))
 
     def add(self, hash):
         """Insert an additional object in the list."""
-        self.also[hash] = 1
-
-    def zap_also(self):
-        """Remove all additional objects from the list."""
-        self.also = {}
+        self.also.add(hash)
 
 
 def calc_hash(type, content):
@@ -399,61 +516,66 @@ def _shalist_sort_key(ent):
         return name
 
 
-def idxmerge(idxlist):
-    """Generate a list of all the objects reachable in a PackIdxList."""
-    total = sum(len(i) for i in idxlist)
-    iters = (iter(i) for i in idxlist)
-    heap = [(next(it), it) for it in iters]
-    heapq.heapify(heap)
-    count = 0
-    last = None
-    while heap:
-        if (count % 10024) == 0:
-            progress('Reading indexes: %.2f%% (%d/%d)\r'
-                     % (count*100.0/total, count, total))
-        (e, it) = heap[0]
-        if e != last:
-            yield e
-            last = e
-        count += 1
-        e = next(it)
-        if e:
-            heapq.heapreplace(heap, (e, it))
+def open_idx(filename):
+    if filename.endswith('.idx'):
+        f = open(filename, 'rb')
+        header = f.read(8)
+        if header[0:4] == '\377tOc':
+            version = struct.unpack('!I', header[4:8])[0]
+            if version == 2:
+                return PackIdxV2(filename, f)
+            else:
+                raise GitError('%s: expected idx file version 2, got %d'
+                               % (filename, version))
+        elif len(header) == 8 and header[0:4] < '\377tOc':
+            return PackIdxV1(filename, f)
         else:
-            heapq.heappop(heap)
-    log('Reading indexes: %.2f%% (%d/%d), done.\n' % (100, total, total))
+            raise GitError('%s: unrecognized idx file header' % filename)
+    elif filename.endswith('.midx'):
+        return PackMidx(filename)
+    else:
+        raise GitError('idx filenames must end with .idx or .midx')
+
+
+def idxmerge(idxlist, final_progress=True):
+    """Generate a list of all the objects reachable in a PackIdxList."""
+    def pfunc(count, total):
+        qprogress('Reading indexes: %.2f%% (%d/%d)\r'
+                  % (count*100.0/total, count, total))
+    def pfinal(count, total):
+        if final_progress:
+            progress('Reading indexes: %.2f%% (%d/%d), done.\n'
+                     % (100, total, total))
+    return merge_iter(idxlist, 10024, pfunc, pfinal)
 
 
+def _make_objcache():
+    return PackIdxList(repo('objects/pack'))
+
 class PackWriter:
     """Writes Git objects insid a pack file."""
-    def __init__(self, objcache_maker=None):
+    def __init__(self, objcache_maker=_make_objcache):
         self.count = 0
         self.outbytes = 0
         self.filename = None
         self.file = None
+        self.idx = None
         self.objcache_maker = objcache_maker
         self.objcache = None
 
     def __del__(self):
         self.close()
 
-    def _make_objcache(self):
-        if self.objcache == None:
-            if self.objcache_maker:
-                self.objcache = self.objcache_maker()
-            else:
-                self.objcache = PackIdxList(repo('objects/pack'))
-
     def _open(self):
         if not self.file:
-            self._make_objcache()
             (fd,name) = tempfile.mkstemp(suffix='.pack', dir=repo('objects'))
             self.file = os.fdopen(fd, 'w+b')
             assert(name.endswith('.pack'))
             self.filename = name[:-5]
             self.file.write('PACK\0\0\0\2\0\0\0\0')
+            self.idx = list(list() for i in xrange(256))
 
-    def _raw_write(self, datalist):
+    def _raw_write(self, datalist, sha):
         self._open()
         f = self.file
         # in case we get interrupted (eg. KeyboardInterrupt), it's best if
@@ -462,15 +584,29 @@ class PackWriter:
         # to our hashsplit algorithm.)  f.write() does its own buffering,
         # but that's okay because we'll flush it in _end().
         oneblob = ''.join(datalist)
-        f.write(oneblob)
-        self.outbytes += len(oneblob)
+        try:
+            f.write(oneblob)
+        except IOError, e:
+            raise GitError, e, sys.exc_info()[2]
+        nw = len(oneblob)
+        crc = zlib.crc32(oneblob) & 0xffffffff
+        self._update_idx(sha, crc, nw)
+        self.outbytes += nw
         self.count += 1
+        return nw, crc
 
-    def _write(self, bin, type, content):
+    def _update_idx(self, sha, crc, size):
+        assert(sha)
+        if self.idx:
+            self.idx[ord(sha[0])].append((sha, crc, self.file.tell() - size))
+
+    def _write(self, sha, type, content):
         if verbose:
             log('>')
-        self._raw_write(_encode_packobj(type, content))
-        return bin
+        if not sha:
+            sha = calc_hash(type, content)
+        size, crc = self._raw_write(_encode_packobj(type, content), sha=sha)
+        return sha
 
     def breakpoint(self):
         """Clear byte and object counts and return the last processed id."""
@@ -478,23 +614,26 @@ class PackWriter:
         self.outbytes = self.count = 0
         return id
 
-    def write(self, type, content):
-        """Write an object in this pack file."""
-        return self._write(calc_hash(type, content), type, content)
+    def _require_objcache(self):
+        if self.objcache is None and self.objcache_maker:
+            self.objcache = self.objcache_maker()
+        if self.objcache is None:
+            raise GitError(
+                    "PackWriter not opened or can't check exists w/o objcache")
 
-    def exists(self, id):
+    def exists(self, id, want_source=False):
         """Return non-empty if an object is found in the object cache."""
-        if not self.objcache:
-            self._make_objcache()
-        return self.objcache.exists(id)
+        self._require_objcache()
+        return self.objcache.exists(id, want_source=want_source)
 
     def maybe_write(self, type, content):
         """Write an object to the pack file if not present and return its id."""
-        bin = calc_hash(type, content)
-        if not self.exists(bin):
-            self._write(bin, type, content)
-            self.objcache.add(bin)
-        return bin
+        self._require_objcache()
+        sha = calc_hash(type, content)
+        if not self.exists(sha):
+            self._write(sha, type, content)
+            self.objcache.add(sha)
+        return sha
 
     def new_blob(self, blob):
         """Create a blob object in the pack with the supplied content."""
@@ -523,12 +662,11 @@ class PackWriter:
         l.append(msg)
         return self.maybe_write('commit', '\n'.join(l))
 
-    def new_commit(self, parent, tree, msg):
+    def new_commit(self, parent, tree, date, msg):
         """Create a commit object in the pack."""
-        now = time.time()
         userline = '%s <%s@%s>' % (userfullname(), username(), hostname())
         commit = self._new_commit(tree, parent,
-                                  userline, now, userline, now,
+                                  userline, date, userline, date,
                                   msg)
         return commit
 
@@ -536,15 +674,18 @@ class PackWriter:
         """Remove the pack file from disk."""
         f = self.file
         if f:
+            self.idx = None
             self.file = None
             f.close()
             os.unlink(self.filename + '.pack')
 
-    def _end(self):
+    def _end(self, run_midx=True):
         f = self.file
         if not f: return None
         self.file = None
         self.objcache = None
+        idx = self.idx
+        self.idx = None
 
         # update object count
         f.seek(8)
@@ -555,33 +696,59 @@ class PackWriter:
         # calculate the pack sha1sum
         f.seek(0)
         sum = Sha1()
-        while 1:
-            b = f.read(65536)
+        for b in chunkyreader(f):
             sum.update(b)
-            if not b: break
-        f.write(sum.digest())
-
+        packbin = sum.digest()
+        f.write(packbin)
         f.close()
 
-        p = subprocess.Popen(['git', 'index-pack', '-v',
-                              '--index-version=2',
-                              self.filename + '.pack'],
-                             preexec_fn = _gitenv,
-                             stdout = subprocess.PIPE)
-        out = p.stdout.read().strip()
-        _git_wait('git index-pack', p)
-        if not out:
-            raise GitError('git index-pack produced no output')
-        nameprefix = repo('objects/pack/%s' % out)
+        obj_list_sha = self._write_pack_idx_v2(self.filename + '.idx', idx, packbin)
+
+        nameprefix = repo('objects/pack/pack-%s' % obj_list_sha)
         if os.path.exists(self.filename + '.map'):
             os.unlink(self.filename + '.map')
         os.rename(self.filename + '.pack', nameprefix + '.pack')
         os.rename(self.filename + '.idx', nameprefix + '.idx')
+
+        if run_midx:
+            auto_midx(repo('objects/pack'))
         return nameprefix
 
-    def close(self):
+    def close(self, run_midx=True):
         """Close the pack file and move it to its definitive path."""
-        return self._end()
+        return self._end(run_midx=run_midx)
+
+    def _write_pack_idx_v2(self, filename, idx, packbin):
+        idx_f = open(filename, 'w+b')
+        idx_f.write('\377tOc\0\0\0\2')
+
+        ofs64_ofs = 8 + 4*256 + 28*self.count
+        idx_f.truncate(ofs64_ofs)
+        idx_f.seek(0)
+        idx_map = mmap_readwrite(idx_f, close=False)
+        idx_f.seek(0, SEEK_END)
+        count = _helpers.write_idx(idx_f, idx_map, idx, self.count)
+        assert(count == self.count)
+        idx_map.close()
+        idx_f.write(packbin)
+
+        idx_f.seek(0)
+        idx_sum = Sha1()
+        b = idx_f.read(8 + 4*256)
+        idx_sum.update(b)
+
+        obj_list_sum = Sha1()
+        for b in chunkyreader(idx_f, 20*self.count):
+            idx_sum.update(b)
+            obj_list_sum.update(b)
+        namebase = obj_list_sum.hexdigest()
+
+        for b in chunkyreader(idx_f):
+            idx_sum.update(b)
+        idx_f.write(idx_sum.digest())
+        idx_f.close()
+
+        return namebase
 
 
 def _git_date(date):
@@ -656,6 +823,33 @@ def rev_get_date(ref):
     raise GitError, 'no such commit %r' % ref
 
 
+def rev_parse(committish):
+    """Resolve the full hash for 'committish', if it exists.
+
+    Should be roughly equivalent to 'git rev-parse'.
+
+    Returns the hex value of the hash if it is found, None if 'committish' does
+    not correspond to anything.
+    """
+    head = read_ref(committish)
+    if head:
+        debug2("resolved from ref: commit = %s\n" % head.encode('hex'))
+        return head
+
+    pL = PackIdxList(repo('objects/pack'))
+
+    if len(committish) == 40:
+        try:
+            hash = committish.decode('hex')
+        except TypeError:
+            return None
+
+        if pL.exists(hash):
+            return hash
+
+    return None
+
+
 def update_ref(refname, newval, oldval):
     """Change the commit pointed to by a branch."""
     if not oldval:
@@ -686,7 +880,10 @@ def guess_repo(path=None):
 def init_repo(path=None):
     """Create the Git bare repository for bup in a given path."""
     guess_repo(path)
-    d = repo()
+    d = repo()  # appends a / to the path
+    parent = os.path.dirname(os.path.dirname(d))
+    if parent and not os.path.exists(parent):
+        raise GitError('parent directory "%s" does not exist\n' % parent)
     if os.path.exists(d) and not os.path.isdir(os.path.join(d, '.')):
         raise GitError('"%d" exists but is not a directory\n' % d)
     p = subprocess.Popen(['git', '--bare', 'init'], stdout=sys.stderr,
@@ -825,6 +1022,7 @@ class CatPipe:
                                   stdin=subprocess.PIPE,
                                   stdout=subprocess.PIPE,
                                   close_fds = True,
+                                  bufsize = 4096,
                                   preexec_fn = _gitenv)
 
     def _fast_get(self, id):
@@ -838,11 +1036,13 @@ class CatPipe:
         assert(not self.inprogress)
         assert(id.find('\n') < 0)
         assert(id.find('\r') < 0)
-        assert(id[0] != '-')
+        assert(not id.startswith('-'))
         self.inprogress = id
         self.p.stdin.write('%s\n' % id)
+        self.p.stdin.flush()
         hdr = self.p.stdout.readline()
         if hdr.endswith(' missing\n'):
+            self.inprogress = None
             raise KeyError('blob %r is missing' % id)
         spl = hdr.split(' ')
         if len(spl) != 3 or len(spl[0]) != 40:
@@ -905,3 +1105,16 @@ class CatPipe:
                 yield d
         except StopIteration:
             log('booger!\n')
+
+def tags():
+    """Return a dictionary of all tags in the form {hash: [tag_names, ...]}."""
+    tags = {}
+    for (n,c) in list_refs():
+        if n.startswith('refs/tags/'):
+            name = n[10:]
+            if not c in tags:
+                tags[c] = []
+
+            tags[c].append(name)  # more than one tag can point at 'c'
+
+    return tags