Retrieve and resolve the reference pointed at by HEAD.
The returned git_reference will be owned by caller and
git_reference_free() must be called when done with it to release the
allocated memory and prevent a leak.
0 on success, git_error_code.GIT_EUNBORNBRANCH when HEAD points to a non existing branch, git_error_code.GIT_ENOTFOUND when HEAD is missing; an error code otherwise
Retrieve and resolve the reference pointed at by HEAD.
The returned git_reference will be owned by caller and git_reference_free() must be called when done with it to release the allocated memory and prevent a leak.