Hi,
The shell-command-to-string calls shell-file-name directly and it doesn't work in the case of local Windows and remoter Unix. I borrow the some code from shell.el and make a patch to simple.el.
Example: in find-file-in-project, shell-command-to-string was called to get the list of filenames. If it is in a remote directry via tramp, it will put error message c:/.../cmdproxy.exe not found.
The patch solves the issue.
Best Regards,
Shuguang