tests/histedit-helpers.sh

largefile: use `self` in repo method instead of `repo`

Most method added (or overwritten) to repo by largefile works on `repo`
instead of `self`. This currently works without trouble because `self` and
`repo` are likely the same. However this is semantically dubious and this may
cause issue for filtering. `self` may be proxy object different from the `repo`
one.

This changeset fix that and use `self` when applicable.

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"
}