rebase: reinstate old-style rev spec support for the source and base (issue3181) As of b12362ab13e7 (first released as part of Mercurial 2.0), the rebase command accepted ONLY revsets for the source and base arguments and no longer accepted old-style revision specifications. As a result, some revision names were no longer recognised, e.g. hg rebase --base br-anch abort: unknown revision 'br'! These arguments are now interpreted first as old-style revision specifications, then as revsets when no matching revision is found. This restores backwards compatibility with releases prior to 2.0.