I asked because none of the posted permutations offer the same feature set. Specifically, the nice thing about this utility (and reason for the dependencies) is interactive adding and selecting of identities. If this can replicated in bash, I am legitimately interested in seeing it, 20 lines or not.
Implement the `git identity` portion listed earlier with a `identity-list` utilizing `git config --get-regexp`. If you need interactivity you can tie it together with fzf and some awk.