I know that when you add a submodule to a git repository it tracks a particular commit of that submodule referenced by its sha1.
I'm trying to find where this sha1 value is stored.
The .gitmodules and .git/config files only show the paths for the submodule, but not the sha1 of the commit.
The git-submodule(1) reference only speaks of a gitlink entry and the gitmodules(5) reference doesn't say anything about this either.
It is stored in Git's object database directly. The tree object for the directory where the submodule lives will have an entry for the submodule's commit (this is the so-called "gitlink").
Try doing git ls-tree master <path-to-directory-containing-submodule> (or just git ls-tree master if the submodule lives in the top-level directory).
来源：https://stackoverflow.com/questions/5033441/where-does-git-store-the-sha1-of-the-commit-for-a-submodule