Run git commands in the Fuchsia tree.
usage: fx git <args> This command delegates to the `git` binary found in the PATH. In a standard checkout, this will be the system git. In a Cog workspace (or other non-standard environment), `fx` may inject a git-polyfill into the PATH (see scripts/cog/git-polyfill/README.md). In that case, this command will invoke the polyfill, allowing `fx git` to work transparently even when a real .git directory is missing.