tests/histedit-helpers.sh

rust-python-testing: separated base test classes

This will allow, e.g., to change `test-rust-discovery.py` simply
by adding the appropriate base class.

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
}