Re: Bug with branches/merges in submodules

> Hello,
> I ran into a bug where commits are omitted from `git submodule summary`
> and friends when the submodule contains merge commits.
> Originally using 2.30.2, I can also reproduce this with a fresh build on the
> `next` branch (see attached bugreport).
> I would assume that this is not intentional, however I cannot find any relevant
> information on this.

> Thank you for filling out a Git bug report!
> Please answer the following questions to help us understand your issue.
> 
> What did you do before the bug happened? (Steps to reproduce your issue)
> Set up a submodule that has branches/merge commits:
> ```bash
> # create repository "child"
> mkdir child-repo
> cd child-repo
> git init
> touch initial.txt
> git add initial.txt
> git commit -m "initial child"
> cd ..
> # create repository "parent"
> mkdir parent
> cd parent
> git init
> # add submodule "child" to repository "parent"
> git submodule add ../child-repo/ child
> git commit -am "initial parent"
> cd child
> # make two commits in separate branches in "child"
> git switch -c "secondary"
> touch s1.txt
> git add s1.txt
> git commit -m "s1"
> git switch master
> touch m1.txt
> git add m1.txt
> git commit -m "m1"
> # merge branch "secondary" into "master" in "child" - this creates a merge commit
> git merge secondary --no-edit
> cd ..
> ```
> Run `git diff --submodule=log` inside the "parent" repository.
> 
> What did you expect to happen? (Expected behavior)
> `git diff --submodule=log` should show all three commits added to the "child"
> submodule:
> ```
> Submodule child XXXXXXX..YYYYYYY
>> Merge branch 'secondary'
>> m1
>> s1
> ```
> 
> What happened instead? (Actual behavior)
> `git diff --submodule=log` only shows commits from one ancestor of the merge
> commit:
> ```
> Submodule child XXXXXXX..YYYYYYY
>> Merge branch 'secondary'
>> m1
> ```
> 
> What's different between what you expected and what actually happened?
> All the commits added to the "secondary" branch are missing in
> `git diff --submodule=log`.
> 
> Anything else you want to add:
> The commit range shown by `git diff --submodule=log` is correct:
> `cd child; git log XXXXXXX..YYYYYYY` shows the correct list of commits.
> 
> This bug also affects `git submodule summary`, and `git show --submodule=log`
> after the changes have been committed.