Re: [PATCH 2/4] push, fetch: error out for submodule entries not pointing to commits

> From: Stefan Beller <sbeller@google.com>
> 
> The check_has_commit helper uses resolves a submodule entry to a
> commit, when validating its existence. As a side effect this means
> tolerates a submodule entry pointing to a tag, which is not a valid
> submodule entry that git commands would know how to cope with.
> 
> Tighten the check to require an actual commit, not a tag pointing to a
> commit.
> 
> Also improve the error handling when a submodule entry points to
> non-commit (e.g., a blob) to error out instead of warning and
> pretending the pointed to object doesn't exist.
> 
> Signed-off-by: Stefan Beller <sbeller@google.com>
> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>