D4055: rebase: move "backup" flag to rbsrt

[pulkit (Pulkit Goyal)]

pulkit added inline comments.

INLINE COMMENTS

> rebase.py:349
> +        nobackup = (not backup) or (not self.backupf)
> +        backup = not nobackup
> +

not A or not B = not (A and B)
not(not A or not B) = A and B

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4055

To: khanchi97, #hg-reviewers
Cc: pulkit, mercurial-devel