revlog: add a _datareadfp context manager for data access needs
The helper handles:
1) is there a file handle already open that we shall just reuse,
2) is the revlog inlined or not.
Using a context manager for all read access will help setting up file pointer
caching in later changesets.
# Dummy extension to define a namespace containing revision names
from __future__ import absolute_import
from mercurial import (
namespaces,
)
def reposetup(ui, repo):
names = {'r%d' % rev: repo[rev].node() for rev in repo}
namemap = lambda r, name: names.get(name)
nodemap = lambda r, node: ['r%d' % repo[node].rev()]
ns = namespaces.namespace('revnames', templatename='revname',
logname='revname',
listnames=lambda r: names.keys(),
namemap=namemap, nodemap=nodemap)
repo.names.addnamespace(ns)