tests/histedit-helpers.sh

revset: refactor parents() into a single return point

Both paths are doing similar thing in the end. We refactor the function so that
the `ps` set is commonly used at the end.

This will end excluding `nullrev` from this set in a future patch

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"
}