rebase: --abort doesn't strip away the target changeset (issue2220)
When a changeset is skipped, rebase keeps the previous target as next
target and if the skipped cset is the first one, the recorded target is
actually the original target.
--abort did not detect this situation but simply stripped away the cset.
adding a
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
% should issue warning
adding a
created new head
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
% should not issue warning
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
marked working directory as branch testing
% should not issue warning