Share file between 2 repositories

Question

Given the 2 following repositories:

webapp-repoA/
    src/
        main/
            java/
            resources/
                toshare/theFile.txt
            webapp/
        test/
    .gitignore

dbRefact-repoB/
    src/
        main/
            java/
            resources/
        test/
    .gitignore

What is the sequence of 'subtree' commands to get the file "toshare/theFile.txt" located in the "webapp-RepoA" repository to be copied to the "resources" folder of the "dbRefact-repoB" repository?

I do not want to create a third repository. Changes to "theFile.txt" will be from the repository "webapp-RepoA". I do not want all the contents of the "webapp-RepoA" repository in the "dbRefact-repoB", only the "toshare/theFile.txt" file.