imerge: fix ancestor calculation If wctx already has two parents, ancestor calculation is wrong. Normally merge is called before wctx gets the second parent, so we simulate this in imerge by temporarily popping the second parent before calling filemerge. Highly dirty. This patch also handles the ParseError move from cmdutil to dispatch.

1 files updated, 0 files merged, 0 files removed, 0 files unresolved
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
(run 'hg update' to get a working copy)
1 files updated, 0 files merged, 1 files removed, 0 files unresolved