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.
bookmarks: Rename --move to --rename
To me, --move sounds like "make an existing bookmark refer to another
revision", but --move currently means "rename an existing bookmark".
This patch renames the switch to --rename to make it easier to
understand.
bookmarks: Only save undo.bookmarks if bookmarks exist
Otherwise the command will abort when there is no .hg/bookmarks file.