"mixed" or "merged" submodules

> Hello,
>
> here  https://stackoverflow.com/q/72770397/1876484
>
> I asked this question:
>
> I'm aware of git submodules which dwell each in its own separate directory.
>
> 1. But is there such thing as "mixed" submodules whose content is
> "merged" together?
>
> For instance:
>
> - Submodule1 (path ./), consist of files `a.txt`, `b.txt` and
> directory `C` with the file `1.txt`
> - Submodule2 (path ./), consist of files `x.txt`, `y.txt` and
> directory `C` with the file `2.txt`
> - Resulting "mixed" repo of both submodules: files `a.txt`, `b.txt`,
> `x.txt`, `y.txt` and directory `C` with the files `1.txt`, `2.txt`
>
> 2. If it is not implemented in git - is there a workaround to achieve this?
>
> Here my use case:
>
> Both submodules - independent libraries (collection of books as plain
> text files), which have same structure (directories = book
> categories). I want to present the combined parent git repository as
> full collection of books, while both projects evolve independently and
> do not overlap (in terms of file names = books).
>
> I got a very detailed and informative answer. My question now - do you
> see any other practical use cases for such a feature? Would such a
> more general case of submodules be a good feature in git or not?

>
>
> On Tue, Jul 05 2022, Sim Tov wrote:
>
> > Hello,
> >
> > here  https://stackoverflow.com/q/72770397/1876484
> >
> > I asked this question:
> >
> > I'm aware of git submodules which dwell each in its own separate directory.
> >
> > 1. But is there such thing as "mixed" submodules whose content is
> > "merged" together?
> >
> > For instance:
> >
> > - Submodule1 (path ./), consist of files `a.txt`, `b.txt` and
> > directory `C` with the file `1.txt`
> > - Submodule2 (path ./), consist of files `x.txt`, `y.txt` and
> > directory `C` with the file `2.txt`
> > - Resulting "mixed" repo of both submodules: files `a.txt`, `b.txt`,
> > `x.txt`, `y.txt` and directory `C` with the files `1.txt`, `2.txt`
> >
> > 2. If it is not implemented in git - is there a workaround to achieve this?
> >
> > Here my use case:
> >
> > Both submodules - independent libraries (collection of books as plain
> > text files), which have same structure (directories = book
> > categories). I want to present the combined parent git repository as
> > full collection of books, while both projects evolve independently and
> > do not overlap (in terms of file names = books).
> >
> > I got a very detailed and informative answer. My question now - do you
> > see any other practical use cases for such a feature? Would such a
> > more general case of submodules be a good feature in git or not?
>
> Good question, but to answer the thought experiment don't conflate
> submodules with this, instead suppose that you have two branches A & B,
> which have:
>
>     A: A.txt
>     B: B.txt
>
> How will you create and maintain a third branch C which has the union of
> the two?
>
> The answer to that question will be the same as with the submodule case,
> i.e. you'd need to have some third branch that you maintain (e.g. with a
> push hook?) that would be a merge of the two, and ensure that you don't
> have path conflicts there.
>
> Then if you wanted to use such a branch as a submodule you'd grab that
> down like you would any other branch.
>