Git Source Ref Option Handling

Treat Git source ref values strictly as references

Terragrunt now passes the ref from a Git module source to git strictly as a reference when downloading through content-addressable storage. Previously a source whose ref began with a git option (for example a value starting with --) could be interpreted by git as an option rather than a reference while fetching the source.

Terragrunt now terminates git option parsing before the repository and reference arguments in its fetch, clone, and ls-remote invocations, so these values can only ever be read as the repository and reference they are meant to be. Normal refs, branches, tags, and commit SHAs continue to work unchanged.