tests/test-merge8.out

bookmarks: Only save undo.bookmarks if bookmarks exist

Otherwise the command will abort when there is no .hg/bookmarks file.

updating working directory
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
(run 'hg update' to get a working copy)
1 files updated, 0 files merged, 1 files removed, 0 files unresolved