tests/histedit-helpers.sh

forget: add --confirm option

Also added confirmopts in cmdutil.py

Differential Revision: https://phab.mercurial-scm.org/D2934

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
}