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.
#!/bin/sh
hg init
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1