bookmarks: Avoid unconditional forwarding of bookmarks for the null revision
This patch fixes the following minor problem:
% hg bookmark -r null test
% hg bookmarks
test -1:000000000000
[...]
% hg commit
% hg bookmarks
* test 17:861ce7a241f9
That is: Bookmarks referring to the null revision are always forwarded
to the current revision.
adding a
abort: username 'foo\nbar1' contains a newline
abort: username 'foo\nbar2' contains a newline
transaction abort!
rollback completed
abort: username 'foo\nbar3' contains a newline!