changelog: make sure datafile is 00changelog.d (API)
0ad0d26ff7 makes it possible for changelog datafile to be "00changelog.i.d",
which is wrong. This patch adds an explicit datafile parameter to fix it.
util: drop unneeded override, sortdict.copy()
OrderedDict.copy() returns self.__class__(self).
drawdag: provide filenode for its dummy filectx
basefctx has filenode, which will be used in a future fast path of skipping
flag processor during repo._filecommit.
This patch adds filenode to drawdag's faked filectx so we don't need to use
hasattr in localrepo.py.