bookmarks: calculateupdate() returns a bookmark, not a rev
This changes the inaccurate/unclear documentation and also changes the
code so "node" now contains a binary nodeid.
Differential Revision: https://phab.mercurial-scm.org/D3087
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.