rev-list with multiple commits sharing same patch-id

[Arnaud Morin <arnaud.morin@gmail.com>]

Hey all,

I am struggling with a rev-list command, hope someone can give me a
clue on what is going on.

I have 2 branches:
$ git branch
  B
* master

Currently on master, there is not diff against B:
$ git diff
(empty)

The commits in B are cherry-picked from master.
Here is the graph:
$ git log --graph --oneline --all
* ae2e3c4 (origin/B, B) remove line2 and add line4 (bis)
* a7a0339 remove line4
* caa4aad restore line2
* d7dc596 remove line2 add line4
* 44bcfd4 add line3
* e372641 b
| * dbf86d8 (HEAD -> master, origin/master) remove line2 and add line4 (bis)
| * 4017282 remove line4
| * 0f2a449 restore line2
| * 8969d3f remove line2 add line4
| * e73b420 add line3
| * fe5a75a b
|/  
* 6192505 a
* b4089e1 init


However, when using git rev-list to perform a symmetric difference, git
is giving me a commit ID:
$ git rev-list --left-right --cherry-pick B...master
>dbf86d8aafc897a25a3093139b4237a62395041e

Note that this commit is not empty
$ git show dbf86d8aafc897a25a3093139b4237a62395041e --stat
commit dbf86d8aafc897a25a3093139b4237a62395041e (origin/master, master)
Author: Arnaud Morin <hidden@mail>
Date:   Sat Jan 9 10:30:10 2021 +0100

    remove line2 and add line4 (bis)

 a | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)



So, from git rev-list perspective, there is a diff.

After digging a little bit, the thing is that this commit is having the
following patch-id:
$ git show dbf86d8aafc897a25a3093139b4237a62395041e | git patch-id
20f4ace68e80a751b07d78a27c94e83d6c5314bc dbf86d8aafc897a25a3093139b4237a62395041e

Which is also already existing in an other commit:
$ for c in $(git rev-list HEAD) ; do git show $c |git patch-id |grep 20f4ace68e80a751b07d78a27c94e83d6c5314bc; done
20f4ace68e80a751b07d78a27c94e83d6c5314bc dbf86d8aafc897a25a3093139b4237a62395041e
20f4ace68e80a751b07d78a27c94e83d6c5314bc 8969d3fa9159730fd3b23199873bfb26e3d20027

So, is it normal that rev-list is not able to figure out that a commit
is existing in both branch when 2 commits share the same patch-id?

Is there any way to prevent rev-list from showing this commit?

Thanks for your help.


PS. I have uploaded my test repo here:
https://gitlab.com/arnaudmorin/git-rev-list


-- 
Arnaud Morin