keyword: (bugfix) only set changenode for kwtemplater when committing
kwexpand must always obtain changenode from filectx,
otherwise current changenode is expanded in every file.
Also fixes "hg cat <more than 1 file>".
adding foo
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
adding foo
rev offset length base linkrev nodeid p1 p2
0 0 0 0 0 b80de5d13875 000000000000 000000000000
1 0 24 0 1 0376abec49b8 000000000000 000000000000