How to make a git submodule just a project folder?

Question

git

There is a project which is stored in GIT.
The project uses several submodules.
myproject
+--dir1
+--dir2
+--dir3 (as git submodule)
+--dir4 (as git submodule)
+--dir5
... You want
to get rid of the submodule, but the dir3 and dir4 folders should remain in the project.
It is required to save the entire history of submodule commits.
How?

Answer 1

Delete the submodule, leaving the folder itself:

git submodule deinit dir3
git rm --cached dir3
rm -rf .git/modules/dir3

Next, add this folder to the index of the current repository:
ps something like this, I did not test it :)

Answer 2

I won’t tell you the exact instructions, but you need to look towards git subtree

Answer 3

More or less like this:

git remote add <name> <submodule_url>
git fetch <name>
git merge -s subtree <name>/<branch>