Forgive the plug for a tool I just made, cfimp, which is a simple but fairly powerful CLI tool for importing spreadsheet-derived data (CSV, TSV etc) into Contentful spaces. It can also be used to update existing entries, link entries to (extant) tags, assets or references, and even publish entries.
It exists because the native Contentful import CLI tool is sparsely documented and requires you to first munge your data to JSON (a JSON structure that the docs don’t explain; you have to first do an export to infer the structure). So this is much easier.
If anyone wants to use it feel free, and reports of issues/suggestions very welcome.