tests/histedit-helpers.sh

bundle2: extract a _payloadchunks method for part

We are preparing streaming capability for part. So the generation of payload
chunk will becomes more complex. We extract this part in its own function before
any changes.

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"
}