Fatal error when unstaging deleted files in `--reset` mode

[ivanross]

This happens on --reset mode, when unstaging deleted file:

fatal: ambiguous argument '<filename>': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

[ivanross]

Reopened because is not fixed.

Step to reproduce:

$ touch newfile
$ git add newfile
$ rm newfile
$ git select-interactive --reset

and select newfile