rust: Keep lazily-initialized Changelog and Manifest log on the Repo object
That way if one of them is accessed multiple times it won’t be reopened
from the filesystem.
Differential Revision: https://phab.mercurial-scm.org/D11406
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2