rebase: provide detailed hint to abort message if working dir is not clean
Detailed hint message is now provided when 'pull --rebase' operation detects
unclean working dir, for example:
abort: uncommitted changes
(cannot pull with rebase: please commit or shelve your changes first)
Added tests for uncommitted merge, and for subrepo support verifying that same
hint is also passed to subrepo state check.
running: init test1
result: None
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: None
running: commit -m commit2 -d 2000-01-02 foo
result: None
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: None
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: None