phabricator: extract logic to print the status when posting a commit This will make it easier to list each commit when folding. That makes the output less confusing because it matches the output of `--confirm` and the revisions listed on the command line. Differential Revision: https://phab.mercurial-scm.org/D8313

phabricator: extract the logic to amend diff properties to a function This will be needed on a separate code path when dealing with folding revisions. And since we know that will involve adding multiple local commmits to the diff properties instead of just one, restructure the logic slightly to allow it. Differential Revision: https://phab.mercurial-scm.org/D8312