amend: refactor commit date handling There's no need to parse a date tuple. Just do it for user option.

test-amend: remove uninteresting fields from log output to deduplicate tests We aren't testing the behavior of obsolescence-based amend.

pull: use opts.get('bookmark') instead of opts['bookmark'] This is done because at places in hgsubversion, we call the function directly. I expect there might be more instances in extensions out there which calls commands.push() directly. So let's not require explicitly passing of bookmark value. The use of opts['bookmark'] was introduced in bad05a6afdc89cc58a2af320698ab29bd8de62d4. Differential Revision: https://phab.mercurial-scm.org/D5484