gix-path improperly resolves configuration path reported by Git

Summary

`gix-path` is a crate of the `gitoxide` project (an implementation of `git` written in Rust) dealing paths and their conversions. Prior to version 0.10.11, `gix-path` runs `git` to find the path of a configuration file associated with the `git` installation, but improperly resolves paths containing unusual or non-ASCII characters, in rare cases enabling a local attacker to inject configuration leading to code execution. Version 0.10.11 contains a patch for the issue. In `gix_path::env`, the underlying implementation of the `installation_config` and `installation_config_prefix` functions calls `git config -l --show-origin` to find the path of a file to treat as belonging to the `git` installation. Affected versions of `gix-path` do not pass `-z`/`--null` to cause `git` to report literal paths. Instead, to cover the occasional case that `git` outputs a quoted path, they attempt to parse the path by stripping the quotation marks. The problem is that, when a path is quoted, it may change in substantial ways beyond the concatenation of quotation marks. If not reversed, these changes can result in another valid path that is not equivalent to the original. On a single-user system, it is not possible to exploit this, unless `GIT_CONFIG_SYSTEM` and `GIT_CONFIG_GLOBAL` have been set to unusual values or Git has been installed in an unusual way. Such a scenario is not expected. Exploitation is unlikely even on a multi-user system, though it is plausible in some uncommon configurations or use cases. In general, exploitation is more likely to succeed if users are expected to install `git` themselves, and are likely to do so in predictable locations; locations where `git` is installed, whether due to usernames in their paths or otherwise, contain characters that `git` quotes by default in paths, such as non-English letters and accented letters; a custom `system`-scope configuration file is specified with the `GIT_CONFIG_SYSTEM` environment variable, and its path is in an unusual location or has strangely named components; or a `system`-scope configuration file is absent, empty, or suppressed by means other than `GIT_CONFIG_NOSYSTEM`. Currently, `gix-path` can treat a `global`-scope configuration file as belonging to the installation if no higher scope configuration file is available. This increases the likelihood of exploitation even on a system where `git` is installed system-wide in an ordinary way. However, exploitation is expected to be very difficult even under any combination of those factors.