phabricator: specify some metadata compatibly with arc

Differential Revision: https://phab.mercurial-scm.org/D3414

contrib/phabricator.py

@@ -68,6 +68,7 b' from mercurial import ('
 )
 from mercurial.utils import (
     procutil,
+    stringutil,
 )
 
 cmdtable = {}
@@ -328,6 +329,19 b' def writediffproperties(ctx, diff):'
     }
     callconduit(ctx.repo(), 'differential.setdiffproperty', params)
 
+    params = {
+        'diff_id': diff[r'id'],
+        'name': 'local:commits',
+        'data': json.dumps({
+            ctx.hex(): {
+                'author': stringutil.person(ctx.user()),
+                'authorEmail': stringutil.email(ctx.user()),
+                'time': ctx.date()[0],
+            },
+        }),
+    }
+    callconduit(ctx.repo(), 'differential.setdiffproperty', params)
+
 def createdifferentialrevision(ctx, revid=None, parentrevid=None, oldnode=None,
                                olddiff=None, actions=None):
     """create or update a Differential Revision