Re: make test Unexpected passes

Ben Woosley [off-list ref] writes:

These know breakages:

ok 50 - rebase -m --onto --root
ok 54 - rebase -m without --onto --root with disjoint history

Have to do with rebasing a root/orphan branch with the -m flag,
which defaults to -- merge=recursive, which is the case the patch fixed.

Here are the necessary changes:
...

Thanks, will squash them in and reword the log message accordingly.

    git-rebase--merge: don't include absent parent as a base

    Absent this fix, attempts to rebase an orphan branch using "rebase -m"
    fails with:

        $ git rebase -m ORPHAN_TARGET_BASE
        First, rewinding head to replay your work on top of it...
        ...
    Note the default rebase behavior does not fail:

        $ git rebase ORPHAN_TARGET_BASE
        First, rewinding head to replay your work on top of it...
        Applying: ORPHAN_ROOT_COMMIT_MSG
        Using index info to reconstruct a base tree...

    A few tests were expecting the old behaviour to forbid rebasing such
    a history with "rebase -m", which now need to expect them to succeed.

    Signed-off-by: Ben Woosley [off-list ref]
    Signed-off-by: Junio C Hamano [off-list ref]