tests/histedit-helpers.sh

run-tests: ignore ENOENT failures when removing old .err results

When the same test runs in multiple threads and the previous run was a
failure, the threads can race to delete the error output. This fixes
that.

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"
}