also output errors when spawnSync fails
also output errors when spawnSync fails

If you execute any git commands on a machine without git (e.g. docker)
you will get "null" as stderr from spawnSync which is not very helpful.

The error field on the other hand will contain something like
"Error: spawnSync git ENOENT" which is also not the most user-friendly
message but might point you in the right direction that git is missing,
Esince NOENT is unix lingo for "error no entry".

kurttheviking/git-rev-sync-js