When a submodule is renamed, git log gives incorrect output:

commit 350ebece9bce8d9c495f9a51e6f5529749c5c3cc (HEAD -> master)
Author:
David Turner <novalis@novalis.org>
Date:   Wed Jan 2 17:09:56 2019 -0500

    move

diff --git a/.gitmodules b/.gitmodules
index da1a767..f4baf2a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,3 @@
-[submodule "mymod"]
-	path = mymod
+[submodule "morx"]
+	path = morx
 	url = ../sub
Submodule mymod 86da4a4...86da4a4 (commits not present)

^-- I expect this last line to tell me that the submodule has been
renamed, rather than that it has changed SHA to the same SHA.

See the attached shell script for a demo of this.  I tested with
b21ebb671bb as well as 2.18 and 2.19.  Thanks to Adam Bliss
<abliss@twosigma.com> for helping to figure out the reproduction steps.