Bug 1633494 - Augment `hg` command used to get commit time r=glandium

`hg` gives us some additional levers to tweak when determining which commits are public and non-public. All the better, because `hg`'s default behavior under a rebase is to preserve the original commit time, so if you rebase a month-old commit on the latest version of central, you might still get the "revision too old" error despite your tree actually being completely up-to-date. Here we replace the original logic with something a little bit more robust to that scenario.

As before, this is a best-effort check that might have false positives or false negatives; this commit doesn't change that, but hopefully it decreases the amount of false positives under `hg`.

Differential Revision: https://phabricator.services.mozilla.com/D74745

python/mozversioncontrol/mozversioncontrol/__init__.py

@@ -323,7 +323,8 @@ class HgRepository(Repository):
 
     def get_commit_time(self):
         return int(self._run(
-            'parent', '--template', '{word(0, date|hgdate)}').strip())
+            'log', '--rev', 'heads(ancestors(.) and not draft())',
+            '--template', '{word(0, date|hgdate)}', '--limit', '1').strip())
 
     def sparse_checkout_present(self):
         # We assume a sparse checkout is enabled if the .hg/sparse file