tests/histedit-helpers.sh

node: replace nullid and friends with nodeconstants class

The introduction of 256bit hashes require changes to nullid and other
constant magic values. Start pushing them down from repository and
revlog where sensible.

Differential Revision: https://phab.mercurial-scm.org/D9465

fixbundle() {
    grep -v 'saving bundle' | grep -v 'saved backup' | \
        grep -v added | grep -v adding | \
        grep -v "unable to find 'e' for patching" | \
        grep -v "e: No such file or directory" | \
    cat
}