gix-path uses local config across repos when it is the highest scope

Summary

gix-path is a crate of the gitoxide project dealing with git paths and their conversions. `gix-path` executes `git` to find the path of a configuration file that belongs to the `git` installation itself, but mistakenly treats the local repository's configuration as system-wide if no higher scoped configuration is found. In rare cases, this causes a less trusted repository to be treated as more trusted, or leaks sensitive information from one repository to another, such as sending credentials to another repository's remote. In `gix_path::env`, the underlying implementation of the `installation_config` and `installation_config_prefix` functions calls `git config -l --show-origin` and parses the first line of the output to extract the path to the configuration file holding the configuration variable of highest scope. It is believed to be very difficult to exploit this vulnerability deliberately, due to the need either to anticipate a situation in which higher-scoped configuration variables would be absent, or to arrange for this to happen. Although any operating system may be affected, users running Apple Git on macOS are much less likely to be affected. This issue has been addressed in release version 0.10.10. All users are advised to upgrade.