Same here. Looks like git returns a error for empty path spec since version 2.16. The behavior to treat empty path spec as . was already deprecated for some versions but now its gone.

It looks like defaulting the location parameter of ls_files (lib.rb line 398) to '.' solves this bug for me, but I do not know whether that is a proper and/or complete fix.

This really was deprecated since git 2.1.6: https://raw.githubusercontent.com/git/git/master/Documentation/RelNotes/2.16.0.txt

An empty string as a pathspec element that means "everything"
i.e. 'git add ""', is now illegal.  We started this by first
deprecating and warning a pathspec that has such an element in
2.11 (Nov 2016).

Judging by this changelog entry, the ix here really is using ..

I've mapped possible code where this could break the code on lib.rb:

• line 104. There is no fix necessary because there is a check for nil values
• line 398. This is where our bug is needs a fix
• line 409. There is no fix necessary because there is a check for nil values
• line 488. There is no check for nil values. But performing the the following local test raises no errors Git.open('.').show. Thus no action is required for this case also.

Thus I'll open a PR fixing the case for line 398.

Any eta on a new version released with this fix?