revlog: create a create `null_item` attribute for V0

This value is currently wrong, but at least it is now -obviously- wrong.

Differential Revision: https://phab.mercurial-scm.org/D10644

mercurial/revlogutils/revlogv0.py

@@ -1,146 +1,147 b''
 # revlogv0 - code related to revlog format "V0"
 #
 # Copyright 2005-2007 Olivia Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 from __future__ import absolute_import
 
 
 from ..node import sha1nodeconstants
 from .constants import (
     INDEX_ENTRY_V0,
 )
 from ..i18n import _
 
 from .. import (
     error,
     node,
     pycompat,
     util,
 )
 
 from . import (
     flagutil,
     nodemap as nodemaputil,
 )
 
 
 def getoffset(q):
     return int(q >> 16)
 
 
 def gettype(q):
     return int(q & 0xFFFF)
 
 
 def offset_type(offset, type):
     if (type & ~flagutil.REVIDX_KNOWN_FLAGS) != 0:
         raise ValueError(b'unknown revlog index flags')
     return int(int(offset) << 16 | type)
 
 
 class revlogoldindex(list):
     entry_size = INDEX_ENTRY_V0.size
+    null_item = (0, 0, 0, -1, -1, -1, -1, node.nullid)
 
     @property
     def nodemap(self):
         msg = b"index.nodemap is deprecated, use index.[has_node|rev|get_rev]"
         util.nouideprecwarn(msg, b'5.3', stacklevel=2)
         return self._nodemap
 
     @util.propertycache
     def _nodemap(self):
         nodemap = nodemaputil.NodeMap({sha1nodeconstants.nullid: node.nullrev})
         for r in range(0, len(self)):
             n = self[r][7]
             nodemap[n] = r
         return nodemap
 
     def has_node(self, node):
         """return True if the node exist in the index"""
         return node in self._nodemap
 
     def rev(self, node):
         """return a revision for a node
 
         If the node is unknown, raise a RevlogError"""
         return self._nodemap[node]
 
     def get_rev(self, node):
         """return a revision for a node
 
         If the node is unknown, return None"""
         return self._nodemap.get(node)
 
     def append(self, tup):
         self._nodemap[tup[7]] = len(self)
         super(revlogoldindex, self).append(tup)
 
     def __delitem__(self, i):
         if not isinstance(i, slice) or not i.stop == -1 or i.step is not None:
             raise ValueError(b"deleting slices only supports a:-1 with step 1")
         for r in pycompat.xrange(i.start, len(self)):
             del self._nodemap[self[r][7]]
         super(revlogoldindex, self).__delitem__(i)
 
     def clearcaches(self):
         self.__dict__.pop('_nodemap', None)
 
     def __getitem__(self, i):
         if i == -1:
-            return (0, 0, 0, -1, -1, -1, -1, node.nullid)
+            return self.null_item
         return list.__getitem__(self, i)
 
     def pack_header(self, header):
         """pack header information in binary"""
         return b''
 
     def entry_binary(self, rev):
         """return the raw binary string representing a revision"""
         entry = self[rev]
         if gettype(entry[0]):
             raise error.RevlogError(
                 _(b'index entry flags need revlog version 1')
             )
         e2 = (
             getoffset(entry[0]),
             entry[1],
             entry[3],
             entry[4],
             self[entry[5]][7],
             self[entry[6]][7],
             entry[7],
         )
         return INDEX_ENTRY_V0.pack(*e2)
 
 
 def parse_index_v0(data, inline):
     s = INDEX_ENTRY_V0.size
     index = []
     nodemap = nodemaputil.NodeMap({node.nullid: node.nullrev})
     n = off = 0
     l = len(data)
     while off + s <= l:
         cur = data[off : off + s]
         off += s
         e = INDEX_ENTRY_V0.unpack(cur)
         # transform to revlogv1 format
         e2 = (
             offset_type(e[0], 0),
             e[1],
             -1,
             e[2],
             e[3],
             nodemap.get(e[4], node.nullrev),
             nodemap.get(e[5], node.nullrev),
             e[6],
             0,  # no side data support
             0,  # no side data support
         )
         index.append(e2)
         nodemap[e[6]] = n
         n += 1
 
     index = revlogoldindex(index)
     return index, None