This fixes a bug that Chris Mason found. As for a test case, I can't think of one. It's a very weird case. Basically, if there is a file listed as changed in the changelog entry, but not showing up in any of the associated manifest entries, hg would abort when trying to create a changeset. Now it just decides the file must not have any versions relevant to the changeset.

#!/bin/sh

hg init
echo "nothing" > a
hg add a
hg commit -m ancestor -d "0 0"
echo "something" > a
hg commit -m branch1 -d "0 0"
hg co 0
echo "something else" > a
hg commit -m branch2 -d "0 0"
HGMERGE=merge; export HGMERGE
hg up -m 1
hg id
grep -Ev ">>>|<<<" a
hg status