$ git submodule update fatal: Needed a single revision Unable to find current revision in submodule path 'vim/bundle/systemverilog'
To resolve the issue :
rm -rf vim/bundle/systemverilog git submodule update
Check your .gimodules, one of mine was an http instead of https, (gitub is https only now). Update to the latest version I find a minimum of git 1.8.5 is required for reliable module checkout.
Solution based on gostais docs.