Test if the ignore rules apply to a given file.
This function simply checks the ignore rules to see if they would apply to the given file. Unlike git_status_file(), this indicates if the file would be ignored regardless of whether the file is already in the index or in the repository.
boolean returning 0 if the file is not ignored, 1 if it is
the file to check ignores for, rooted at the repo's workdir.
0 if ignore rules could be processed for the file (regardless of whether it exists or not), or an error < 0 if they could not.