git submodules with only 1 directory?

i need something like git submodules,开发者_运维问答 but the submodule have to be a directory of another project, rather than the entire project.

For example

The Submodule has:

somedir
   files
   dirs
someotherdir
   files
   dirs
thewanteddir
   files
   dir

I want to link thewanteddir with another project

Is there anything that works like that?

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If somedir, someotherdir and thewanteddir are already part of one repo, then you cannot directly see just thewanteddir (At best you would the 'theSubmoduleRootDir/thewanteddir' anyway)
(And shallow clone submodules wouldn't isolate just one subdirectory)

The cleanest solution (but not the easiest one) would be to split that submodule repo in two, and make thewanteddir its own repo (which you can then add as a submodule)

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You could use git-subtree to split off a branch that just has the history of the thewanteddir subdirectory, and then set that commit to be the submodule version. (You'd need to keep using git-subtree to update the submodule, and merge back in changes.)