> We assume familiarity with grep options. The -e option of grep takes an
> argument, namely the pattern to search for. You can either add your
> option before the -e, or maybe you are interested in M-x rgrep.
> I don't see this as an Emacs bug.

aka `M-x man RET grep RET'

That shows:

grep  [OPTIONS]  [-e  PATTERN   |   -f   FILE]  [FILE...]