From the creation of this diff, and hence using this code:
```
Updating commit message...
>>> [115] <conduit> differential.getcommitmessage() <bytes = 145>
>>> [116] <http> https://secure.phabricator.com/api/differential.getcommitmessage
<<< [116] <http> 244,801 us
<<< [115] <conduit> 245,048 us
>>> [117] <exec> $ git commit --amend --allow-empty -F '/tmp/2ohlrfe9wd44cckg/27827-KGfRfo'
<<< [117] <exec> 10,387 us
>>> [118] <exec> $ git rev-parse 'HEAD'
<<< [118] <exec> 5,456 us
>>> [119] <exec> $ git merge-base 'fad85844314b151994769a461825c90f7400c145' 'fb0188dc55bf193410e7f2ff38534c9dcf1daa47'
<<< [119] <exec> 4,646 us
>>> [120] <exec> $ git log 'fb0188dc55bf193410e7f2ff38534c9dcf1daa47' --not 'fad85844314b151994769a461825c90f7400c145' --format='%H%x01%T%x01%P%x01%at%x01%an%x01%aE%x01%s%x01%s%n%n%b%x02' --
<<< [120] <exec> 4,459 us
>>> [121] <conduit> differential.setdiffproperty() <bytes = 1,673>
>>> [122] <http> https://secure.phabricator.com/api/differential.setdiffproperty
```
On the diff, "Commits" contains fb0188dc55bf, and that matches the local commit object:
```
$ git format-patch --stdout -1 | head -n4
From fb0188dc55bf193410e7f2ff38534c9dcf1daa47 Mon Sep 17 00:00:00 2001
From: Alex Vandiver <alexmv@dropbox.com>
Date: Wed, 9 Nov 2016 12:29:19 -0800
Subject: [PATCH] Update the "local:commits" property after amending
```