If the initial commit is empty, it is not shown in "git log --simplify-by-decoration"

Hello,

This seems like a bug to me, but maybe there's a good reason for it. I reproduced it using Git 2.27.0 on Windows initially, and then I upgraded to 2.31.1 to confirm that it was still present.

After committing with "--allow-empty", the initial commit is not shown in "git log --simplify-by-decoration", although it is shown with "git log". I would have expected it to be shown in both cases:

--- $ git init Initialized empty Git repository in C:/tmp/repro/.git/

$ git commit --allow-empty -m init [master (root-commit) bc54978] init

$ git log --simplify-by-decoration

$ git log
commit d7814029effeb7e824e480ca52e30f5a9d1e8058 (HEAD -> master)
Author: mtkennerly <mtkennerly@gmail.com>
Date:   Fri Apr 16 19:48:06 2021 -0400

    init
---

However, if the first commit is not empty, then it is shown with or without "--simplify-by-decoration", as expected:

--- $ git init Initialized empty Git repository in C:/tmp/repro2/.git/

$ echo hi > foo.txt

$ git add .

$ git commit -m init
[master (root-commit) 35b6427] init
 1 file changed, 1 insertion(+)
 create mode 100644 foo.txt

$ git log --simplify-by-decoration
commit 35b6427461fe48c0e918dfea2bc5ddab9dc8844d (HEAD -> master)
Author: mtkennerly <mtkennerly@gmail.com>
Date:   Fri Apr 16 19:51:06 2021 -0400

    init

$ git log
commit 35b6427461fe48c0e918dfea2bc5ddab9dc8844d (HEAD -> master)
Author: mtkennerly <mtkennerly@gmail.com>
Date:   Fri Apr 16 19:51:06 2021 -0400

    init
---

For context, this was reported to me on GitHub here: https://github.com/mtkennerly/dunamai/issues/14

Regards,

MTK