convert: option to set date and time for svn commits Converting to subversion repository is not preserving original commit dates as it may break some subversion functionality if commit dates are not monotonically increasing. This patch adds `convert.svn.dangerous-set-commit-dates` configuration option to change this behaviour and enable commit dates convertion for those who want to take risks. Subversion always uses commit dates with UTC timezone, so only timestamps are used. Test `test-convert-svn-sink.t` uses `svnxml.py` script to dump history of svn repositories. Atm the script is not printing `date` field from svn log. This patch changes this to allow checks on correctness of date and time convertion. Documentation is updated. Additional test case is added to test commit dates convertion. Differential Revision: https://phab.mercurial-scm.org/D9721