RE: grep command doc - point out that you can chain now

[Drew Adams]

     >     I don't think it should be pointed out in the manual
     >     because you would expect it to work.
     >
     > It never occurred to me, so I think it is worth mentioning in the
     > Emacs Manual.  I will add it to the manual.

    Probably because you knew it didn't work in the past.

Yes, I said that myself.

And, I added, also because what you type is apparently not the arguments to
the Unix/GNU-Linux `grep' command, but something possibly much richer. Even
if someone were not used to Emacs 20 `grep' behavior, if s?he were used to
the Unix/GNU-Linux `grep' command, then s?he would expect to be inputting
just the `grep' args, no?

    It still doesn't work for users with versions of grep which don't
    have the -H option, so they will be confused by your description.

Do you mean Eli's description? I didn't describe it, beyond mentioning
piping. Eli gave a real description of what's going on, presumably.

I didn't know that either (-H), BTW. That too is worth pointing out. IOW,
what you type is different for different `grep's - in one case it is the
`grep' args; in another case it is "_any_ shell command whose output
resembles that of Grep."

Those behavior differences are certainly worth pointing out, unless they are
part of the `grep -H' doc. IOW, is what you type the expected arguments for
`grep -H', or is it something special that Emacs (only) allows? Does
`grep -H'  _itself_ allow "_any_ shell command whose output resembles that
of Grep."?

If this is part of the behavior of `grep -H' itself, then I guess it
wouldn't need to be documented in Emacs. It's not clear to me what the story
is. When I do `M-x man RET grep', and look for -H, it says "Print the
filename for each match." That can't be what this is about, can it? Yet,
with that same `grep' (it says "GNU Project 2002/01/22" in the footer), I
get the magical piping. Isn't some explanation necessary? Is this an Emacs
`grep' feature or a Unix/GNU-Linux `grep' feature that Emacs manifests?