Is there a way to specify a git path in the "paths" cargo configuration key ?
And BTW I think the note at the bottom of 3.1.1. ("Overriding dependencies") in the Rust Book might be erroneous/obsolete/misleading : I'm able to override git dependencies with local just fine even when the crate has not been published to crates.io
by "git path", if you mean a URL to a remote git repo, the answer is no, the "paths" config only allows local directories.
I didn't test this, if you think the doc doesn't reflect the current behavior, you can suggest a change and submit a PR. there are links to the repository on the top right corner of the page.