tests/histedit-helpers.sh

baseset: drop custom __sub__ method

This add method is enforcing non-laziness, disabling multiple optimisations.

Benchmarks do not spot any significant difference but real usecase may. This
will also be important for further improvements to addset later in this series.

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"
}