Pass `--update-head-ok` when fetching via git CLI
Pass `--update-head-ok` when fetching via git CLI

Discovered in a recent [comment] it looks like not passing this may
cause the git CLI to fail in some situations.

[comment]: https://github.com/rust-lang/cargo/issues/2078#issuecomment-435333292

nipunn1313/cargo,nipunn1313/cargo,tshepang/cargo,vojtechkral/cargo,nipunn1313/cargo,eminence/cargo,tshepang/cargo,rustyhorde/cargo,tshepang/cargo,tshepang/cargo,rustyhorde/cargo,rustyhorde/cargo,rust-lang/cargo,nipunn1313/cargo,tsurai/cargo,eminence/cargo,vojtechkral/cargo,tsurai/cargo,vojtechkral/cargo,rust-lang/cargo,tsurai/cargo,vojtechkral/cargo,tsurai/cargo,eminence/cargo,eminence/cargo,rust-lang/cargo,rustyhorde/cargo,tsurai/cargo,rust-lang/cargo