bug#6553: M-x grep should encourage the user to remember to add filenames to the command line

[jidanni]

M-x grep, instead of prompting like:
  Run grep (like this): zgrep -nH -e
should prompt like:
  Run grep (like this): zgrep -nH -e    *
with the cursor placed                ^here.
That way the user won't need to remember to add the *, which he usually
wants, but always forgets, as I recall I mentioned a few years back.