format-patch on empty commit

Hi all,

Couldn't find any explanation on git docs on this issue:

If I create a dummy commit, with some dummy diff, I get a normal patch
when I run

$ git format-patch -1 -o outgoing/ -p -k

but if the last commit is an empty commit, generated by

$ git commit --allow-empty "Some commit message"

then the output of the format patch will be an empty patch. If the
first case produces something like this:

From 08cfdb2994554d834b89309ca96d9bf513e26a90 Mon Sep 17 00:00:00 2001

From: pedrorijo91 <redacted>
Date: Fri, 8 Jan 2016 12:44:57 +0000
Subject: dummy commit

diff --git a/lol.txt b/lol.txt
new file mode 100644
index 0000000..f944b38
--- /dev/null
+++ b/lol.txt

@@ -0,0 +1 @@
+:)
--

2.5.4 (Apple Git-61)



then the second case shouldn't generate something like this instead ?

From 2d486f25c48780e2e132047e681929fcccb7e60c Mon Sep 17 00:00:00 2001

From: pedrorijo91 <redacted>
Date: Fri Jan 8 12:43:55 2016 +0000
Subject: Some commit message


2.5.4 (Apple Git-61)



-- 
Thanks,
Pedro Rijo